Modern Slavery, Skilled Workers and the Correct Mechanism: What the New SW 18.3 Concession Does — and Does Not — Do

12 September 2026 by Jawad Bhatti

The application of the Modern Slavery Act 2015, the Coroners and Justice Act 2009 and the Supreme Court jurisprudence of 2017 and 2022 to Skilled Worker cases

Immigration, Modern Slavery and Employment Practice — general information only; not legal advice on any specific case.

Summary

This article sets out the correct legal mechanism governing the interaction between modern slavery status and the Skilled Worker route, anchored in the Coroners and Justice Act 2009, the Modern Slavery Act 2015 and Article 4 of the European Convention on Human Rights. It explains the route through the National Referral Mechanism, the threshold at the Conclusive Grounds stage, and the settled jurisprudence of the Supreme Court in Reyes v Al-Malki [2017] UKSC 61 and Basfar v Wong [2022] UKSC 20, before considering how the new Immigration Rules concession at paragraph SW 18.3 of Appendix Skilled Worker (inserted by Statement of Changes HC 584, laid 3 September 2026 and in force from 8 October 2026) sits within that framework.

The core conclusion is uncomfortable but unavoidable. Non-payment of wages, unpaid holiday, unlawful deductions, breach of contract and generalised workplace mistreatment will not, standing alone, cross the threshold for a positive Conclusive Grounds decision, and will not therefore trigger SW 18.3 relief. The rule is aimed at genuine victims of servitude, forced or compulsory labour, or trafficking for exploitation. The Home Office will not concede outside those parameters.

Part One: Overview

Some preliminary overviews correctly identified the statutory framework and the prospect of a narrow rather than expansive route. On further analysis, several points merit development before that overview is relied upon in advice.

1.1 The effect of the Nationality and Borders Act 2022 changes

The raised Reasonable Grounds threshold under section 58 of the Nationality and Borders Act 2022 operates through objective factors evidenced by specified information, and this has produced a measurable increase in negative RG decisions since January 2023. In practical terms, a referral that would have secured an RG decision in 2021 will not necessarily do so today. Advisers must front-load the evidential effort accordingly. On the other hand, decision-making timescales have improved markedly: median waiting times for a Conclusive Grounds decision fell from over two years in 2024 to around 53 days by March 2026, which materially changes the sequencing calculus discussed below.

1.2 The sponsor duties intersection

The interaction between a sponsor's reporting duties and a worker's prospective SW 18.3 application is delicate. If the sponsor reports the worker as absent, or if the sponsor licence is revoked, the worker's permission may be curtailed before SW 18.3 can be invoked. The correct advice is to sequence any move so that the SW 18.3 application follows the Conclusive Grounds decision and, so far as possible, precedes any curtailment notice. Part 3 of the Workers and Temporary Workers: Guidance for Sponsors (compliance duties, activity reports within 10 working days, and change of circumstances reports) and the 60-day cure period that ordinarily follows sponsor licence revocation are the practical mechanics that govern this sequencing.

1.3 The role of civil claims

Modern slavery is not only an immigration and criminal concept. The modern statutory framework developed in the wake of documented abuse in domestic work settings, with the Strasbourg jurisprudence beginning with Siliadin v France in 2005 and the first domestic prosecutions under section 71 of the Coroners and Justice Act 2009 culminating in R v SK [2011] EWCA Crim 1691. Confirmed victims routinely pursue civil claims for trafficking in tort, unlawful means conspiracy, and Article 4 ECHR claims under the Human Rights Act 1998 where a public body is engaged. In parallel with any SW 18.3 relief, the practitioner should always evaluate ET1 claims under the Employment Rights Act 1996, the National Minimum Wage Act 1998, the Working Time Regulations 1998, and the Equality Act 2010.

1.4 The diplomatic immunity dimension

For Skilled Workers in diplomatic households, or in households connected to accredited missions, the Supreme Court jurisprudence in Reyes v Al-Malki and Basfar v Wong governs whether a civil claim can be brought at all. That dimension is addressed in Part Five below and is important for the small but growing cohort of care workers, drivers, chefs and domestic staff placed with accredited households under the Skilled Worker route or under the Overseas Domestic Worker visa.

1.5 The credibility risk

Where a client presents an NRM referral principally to unlock SW 18.3 relief, and where the underlying facts do not credibly cross the modern slavery threshold, a negative Conclusive Grounds decision will follow. That negative decision then becomes a matter of record and can be used against the client in subsequent immigration applications, particularly on credibility. Practitioners must be alert to this risk and must not encourage referrals for tactical reasons.

Part Two: The Legislative Framework

2.1 Coroners and Justice Act 2009, section 71

Section 71 of the Coroners and Justice Act 2009 created the first free-standing offence in England and Wales of holding another person in slavery or servitude, or requiring another person to perform forced or compulsory labour. It was repealed and replaced for conduct on or after 31 July 2015 by section 1 of the Modern Slavery Act 2015. It remains relevant in two respects. First, for historic conduct predating 31 July 2015 it continues to apply. Second, its interpretive engine imports the meaning of the concepts from Article 4 ECHR and the settled Strasbourg jurisprudence, which continues to inform the meaning of section 1 of the 2015 Act.

2.2 Modern Slavery Act 2015

Section 1 criminalises slavery, servitude and forced or compulsory labour, and requires the concepts to be construed in accordance with Article 4 ECHR. Servitude, in this context, denotes a person compelled to provide labour or services through psychological or physical coercion, threats, or the withholding of documents, without any formal legal ownership of the person. Section 2 criminalises human trafficking and applies whether or not the victim consents, whether or not the exploitation occurs, and whether or not the movement is international. Section 3 defines exploitation exhaustively, including sexual exploitation, removal of organs, forced services, and services obtained from children and vulnerable persons. Section 45 provides a limited statutory defence for victims compelled to commit certain offences. Section 49 requires the Secretary of State to issue statutory guidance on identification and support.

2.3 Article 4 of the European Convention on Human Rights

Article 4 ECHR prohibits slavery, servitude and forced or compulsory labour. The Strasbourg Court has read into Article 4 a positive operational duty on the State to identify and protect victims, and to have in place criminal law and administrative procedures adequate to the task. The controlling authorities are Siliadin v France (2006) 43 EHRR 16 (judgment of 26 July 2005), Rantsev v Cyprus and Russia (2010) 51 EHRR 1, CN v United Kingdom (2012) 56 EHRR 24, and Chowdury v Greece (App no 21884/15, 30 March 2017).

Quick comparison of the jurisprudence:

Siliadin v France (2005) — domestic servitude of a migrant minor. Confirmed Article 4 applies as between private individuals, not just state actors; distinguished "servitude" from "forced labour".
Rantsev v Cyprus and Russia (2010) — sex trafficking and subsequent death of a young woman. Brought human trafficking expressly within Article 4; established strict positive obligations to investigate.
CN v United Kingdom (2012) — domestic servitude of a migrant caregiver. States must have specific criminal legislation targeting modern slavery, rather than relying on general assault or theft offences.
Chowdury v Greece (2017) — exploitation of undocumented migrant strawberry pickers. Extended Article 4 to large-scale agricultural exploitation; absence of physical restraint does not make work voluntary.

2.4 The Nationality and Borders Act 2022

Sections 58 to 65 raised the Reasonable Grounds threshold, codified the public order disqualification, and put on a statutory footing the Victims of Trafficking Discretionary Leave route. The 2022 Act is now the immediate legislative backdrop against which NRM decisions are made.

2.5 The Illegal Migration Act 2023 and its partial repeal

The position under the Illegal Migration Act 2023 has changed materially. Sections 16 to 28 of the 2023 Act, including section 22 (which would have disapplied most modern slavery protections for those within the removal duty), were repealed with effect from 2 December 2025 by the Border Security, Asylum and Immigration Act 2025. What survives is section 29, which strengthens the public order disqualification in section 63 of the Nationality and Borders Act 2022, including in respect of persons liable to deportation. The practical screening exercise for the practitioner is therefore no longer under section 22, but under the public order and bad faith disqualifications in section 63 NABA 2022 as amended. Practitioners should also monitor the Immigration and Asylum Bill 2026, which proposes further amendment of the Modern Slavery Act 2015 and the Nationality and Borders Act 2022.

2.6 The Immigration Rules: SW 18.3

The new rule is Appendix Skilled Worker, paragraph SW 18.3, inserted by Statement of Changes HC 584 (laid 3 September 2026, in force 8 October 2026). The rule provides that a Skilled Worker who has been referred into the National Referral Mechanism and is in receipt of a positive Conclusive Grounds decision, where that decision was made during their most recent permission, may have the conditions in SW 18.2(b) to (e) amended, such that any work — including self-employment and voluntary work — is permitted, except for work as a professional sportsperson (including as a sports coach). It is a work-conditions concession, not a leave extension: the worker is freed from the tie to the sponsoring employer for the remaining duration of their existing permission, and no more.

Part Three: The Correct Mechanism through the National Referral Mechanism

The National Referral Mechanism is the administrative process by which potential victims of modern slavery are identified and supported. It is not a self-referral scheme for adults. The stages, and the downstream consequences of a positive Conclusive Grounds decision, are as follows.

3.1 First Responder referral

A referral must be made by a designated First Responder. The categories include the police, the National Crime Agency, the Home Office (Immigration Enforcement, UK Visas and Immigration and Border Force), local authorities, and a defined list of specified charities including Barnardo's, Migrant Help, the Medaille Trust, the Salvation Army, Unseen, Kalayaan, the Refugee Council and others. See the Home Office statutory guidance under section 49 of the Modern Slavery Act 2015 for the current list.

3.2 Reasonable Grounds decision

The Competent Authority makes a Reasonable Grounds decision on the basis of the referral and any supporting information. Following section 58 of the Nationality and Borders Act 2022, the test is whether there are objective factors, evidenced by specified information, which indicate that the person is a victim. A positive RG decision opens the recovery period (currently a minimum of 30 days), during which the victim is entitled to support and is protected from removal.

3.3 Conclusive Grounds decision

The CG decision applies the balance of probabilities standard to all information gathered. It is made by the Single Competent Authority or the Immigration Enforcement Competent Authority. It is a decision of public importance and is amenable to judicial review on rationality and procedural grounds: R (MN and IXU) v Secretary of State for the Home Department [2020] EWCA Civ 1746, a landmark Court of Appeal judgment which, building directly on the Strasbourg jurisprudence, translates the State's positive procedural obligations under Article 4 ECHR into concrete domestic evidentiary rules. A CG decision is not the same as a criminal conviction; the criminal and civil courts are not bound by it, though it is highly probative.

3.4 Downstream consequences

A positive CG decision opens the doors to Victims of Trafficking Discretionary Leave under section 65 of the Nationality and Borders Act 2022, to Victim Care Contract support, to civil claims in tort and under Article 4 ECHR where a public body is engaged, and, from 8 October 2026 and where the conditions are met, to SW 18.3 relief. A negative CG decision must be challenged promptly, and in any event within three months, by way of judicial review if it is to be resisted.

Part Four: The Threshold and the Non-Payment Question

4.1 The statutory concepts

Slavery is ownership-like control over a person. Servitude, per Siliadin, is a particularly serious form of denial of freedom, including the obligation to provide services and the impossibility of altering that condition. Forced or compulsory labour, per Van der Mussele v Belgium (1983) 6 EHRR 163, means work exacted under the menace of any penalty for which the person has not offered themselves voluntarily.

4.2 The ILO indicators

The Home Office guidance uses the International Labour Organisation indicators as the practical decision tool: abuse of vulnerability; deception; restriction of movement; isolation; physical and sexual violence; intimidation and threats; retention of identity documents; withholding of wages; debt bondage; abusive working and living conditions; and excessive overtime. No single indicator is decisive. The assessment is cumulative and contextual.

4.3 The critical answer on non-payment of wages and holiday

The direct question is whether non-payment of wages, unpaid holiday, or generic contractual exploitation is sufficient to secure a positive CG decision and consequently to trigger SW 18.3 relief. The answer, on the current statutory guidance and the settled case law, is no. These matters, however serious in Employment Tribunal terms, are labour law breaches. They become modern slavery only when they are the mechanism, or a mechanism, of coercive control, deception or abuse of vulnerability that removes the worker's genuine freedom of choice.

A practitioner heuristic on the threshold for CG decisions:

15% underpayment for six months; ACAS complaint made — employment claim, not modern slavery.
Passport retained, movement controlled, threats to family abroad, isolation, and wages withheld as a mechanism of control — positive CG very likely.
Inflated recruitment fees and repayment agreements leaving effectively nil pay, coupled with threats of reporting to the Home Office — potential positive CG on debt bondage plus means.
70-hour weeks under threat of sponsor licence withdrawal and eviction from tied accommodation — likely positive CG on menace of penalty.
Three months' unpaid salary; disputed holiday entitlement; sponsor licence revoked; no coercion — unlikely modern slavery; pursue ET and immigration remedies.
Any other contractual exploitation or non-adherence to the terms and conditions of the contract of employment — unlikely modern slavery; pursue ET, civil, or other immigration remedies.

4.4 The controlling case law

In R v SK [2011] EWCA Crim 1691, the Court of Appeal held that servitude and forced or compulsory labour require conditions that go beyond exploitative employment; there must be an element of compulsion and a lack of any real alternative. In Chowdury v Greece the Strasbourg Court held that migrant strawberry pickers who were underpaid and threatened were victims of forced labour under Article 4, showing that severe underpayment combined with credible threats and abuse of vulnerability crosses the line. In Hounga v Allen [2014] UKSC 47, the Supreme Court recognised the intersection between trafficking and employment discrimination and confirmed the complementarity of the regimes; it addresses the intersection of modern slavery, employment law, and civil justice. In MS (Pakistan) v SSHD [2020] UKSC 9, the Supreme Court confirmed that Home Office decisions engaging modern slavery must be Convention-compliant and cannot be short-circuited.

Part Five: The Supreme Court Jurisprudence of 2017 and 2022

5.1 Reyes v Al-Malki [2017] UKSC 61

Ms Reyes, a Philippine national, alleged that she had been trafficked into the United Kingdom to work in the London home of a Saudi diplomat. She said her passport had been retained, that she was forbidden to leave, was made to work excessive hours without payment and was mistreated. She brought proceedings in the Employment Tribunal. By the time the case reached the Supreme Court, the diplomat had left post.

The Court held unanimously that because the diplomat was no longer in post only the residual immunity in Article 39(2) of the Vienna Convention on Diplomatic Relations applied, and that the alleged mistreatment of a domestic servant in the diplomat's private residence was not an act performed in the exercise of his functions as a member of the mission. The claim could therefore proceed. The obiter reasoning on Article 31(1)(c) VCDR (the commercial activity exception) was divided and set the stage for Basfar.

5.2 Basfar v Wong [2022] UKSC 20

Ms Wong, a Philippine national, alleged that she had been trafficked into the United Kingdom to work for a Saudi diplomat still in post. Her passport had been taken, she had been confined to the residence, made to work approximately sixteen hours a day, seven days a week, and paid a small fraction of what she had been promised. She had escaped, was referred through the NRM, and received a positive Conclusive Grounds decision confirming her as a victim of trafficking for domestic servitude. The case reached the Supreme Court by way of the first leapfrog appeal ever certified from the Employment Appeal Tribunal.

By a majority of three to two (the joint judgment of Lord Briggs and Lord Leggatt, with whom Lord Stephens agreed; Lord Hamblen and Lady Rose jointly dissenting), the Court held that keeping a domestic worker in conditions of modern slavery was a commercial activity within Article 31(1)(c) VCDR, and that immunity therefore did not attach. The reasoning proceeded on the following principles:

The concept of commercial activity in the VCDR must be interpreted in the light of the object and purpose of the Convention and other international obligations, including Article 4 ECHR and ECAT.
Ordinary employment of a domestic servant, even on unfavourable terms, is not a commercial activity; it is incidental to the diplomat's private residential life.
The exploitation of a domestic servant in conditions amounting to modern slavery is qualitatively different: the relationship ceases to be an ordinary contract of employment and becomes an enterprise from which the household extracts a systematic financial gain by the appropriation of labour without paying its value, placing it within Article 31(1)(c).
This interpretation is consistent with the United Kingdom's obligations under Article 4 ECHR and ECAT to provide effective remedies to victims; immunising a diplomat who had trafficked and exploited a domestic worker would sit uneasily with the operational duty recognised in Rantsev.
The trigger for the commercial activity exception is not the mere presence of an employment contract, nor unpaid wages or unfavourable terms; it is conduct crossing the threshold of servitude or forced or compulsory labour within the Article 4 jurisprudence. This directly answers the question whether non-payment of wages alone crosses the threshold: it does not.

5.3 The dissent and its practical consequence

Lord Hamblen and Lady Rose would have held that commercial activity in Article 31(1)(c) had a settled international meaning that did not extend to the employment of a domestic servant, however performed. Their reasoning is important because it warns practitioners that further Vienna Convention arguments in different fact patterns cannot be assumed to succeed. Each case will turn on whether the facts credibly cross the Article 4 threshold.

5.4 The unified principle from 2017 and 2022

Taken together, the two decisions establish that (a) diplomatic immunity is not absolute; (b) once the diplomat leaves post, functional immunity does not shield the abuse of a domestic worker in the private residence; (c) even for serving diplomats, immunity falls away when the facts cross into modern slavery under Article 4 ECHR; and (d) the distinguishing feature between an ordinary employment dispute and modern slavery is the presence of coercion, exploitation of vulnerability and systematic appropriation of labour without payment. This is the same distinction that governs the NRM decision on Conclusive Grounds and therefore the availability of SW 18.3 relief.

Part Six: Home Office Concessions in Practice

6.1 SW 18.3 discretion

SW 18.3 is expressed as a discretion ("may have the conditions… amended", not "shall"). Home Office guidance due before 8 October 2026 will explain how the discretion is exercised. The Explanatory Memorandum to HC 584 frames the change as intended to incentivise victims to come forward early and to guard against those who seek to weaponise the sponsorship system in order to exploit vulnerable workers. Expect the guidance to require: (a) a valid positive CG decision unmodified by challenge; (b) the CG decision to have been made during the worker's most recent permission; (c) the applicant not to be excluded on public order grounds under section 63 of the Nationality and Borders Act 2022 as amended; and (d) the discretion to be exercised on work conditions only, not on leave extension. The prohibition on work as a professional sportsperson or sports coach remains in all cases.

6.2 The near-miss trap

The clearest concession trap is the CG decision made under an earlier grant of leave. On the face of SW 18.3, which requires the decision to have been made during the worker's most recent permission, that worker is not within the rule. There is no near-miss concession, and the Home Office is unlikely to create one. The practical response is either to consider a fresh referral where further exploitation has occurred during the current permission, or to pivot to Victims of Trafficking Discretionary Leave.

6.3 Victims of Trafficking Discretionary Leave

VTS Discretionary Leave, codified in section 65 of the Nationality and Borders Act 2022 and operationalised by Home Office guidance, may be granted where necessary to assist recovery, to enable cooperation with an investigation, or to enable the pursuit of compensation. It is a separate concessionary route and remains available where SW 18.3 does not bite. The Home Office has also accepted that a confirmed victim holding Skilled Worker leave may apply to vary that leave to VTS leave. Grants are typically limited to 30 months and are increasingly scrutinised.

6.4 What the Home Office will not concede

The Home Office will not, in the ordinary case, concede SW 18.3 relief without a positive CG decision. It will not concede VTS Discretionary Leave for pure employment disputes. It will not accept that non-payment of wages, unpaid holiday or generic contractual mistreatment is modern slavery. The message to a client is the difficult one: the correct route for those grievances is the Employment Tribunal, HMRC National Minimum Wage enforcement and the Gangmasters and Labour Abuse Authority, not the NRM.

Practitioner Toolkit and Sequencing

The following sequencing represents current best practice for a solicitor advising a Skilled Worker who reports exploitation.

Immediate safeguarding: safe accommodation and connection with a specialist support provider under the Modern Slavery Victim Care Contract.
First Responder engagement: referral into the NRM through the police, local authority safeguarding, the Salvation Army, Migrant Help or Kalayaan. Adults cannot self-refer.
Preserve immigration status: do not resign from the sponsor before the strategy is settled; carry out a curtailment risk analysis.
Build the modern slavery evidence pack: chronology of coercion; ILO indicators mapped to the facts; medical or psychological evidence; communications evidence; contracts, payslips, right-to-work checks, tied accommodation documents; witness statements.
Parallel employment claim: ACAS Early Conciliation; ET1 within three months less one day; HMRC National Minimum Wage report; GLAA referral where the sector is licensed.
Sponsor licence dimension: consider a UKVI sponsor compliance report; anticipate a possible revocation and the 60-day cure period.
Post-CG immigration application: if a positive CG decision is issued during the current permission, prepare an SW 18.3 application; if not, evaluate VTS Discretionary Leave and Article 8 ECHR alternatives.
Civil recovery: consider trafficking in tort, unjust enrichment, and Article 4 ECHR claims where a public body is engaged; consider limitation and forum.
Diplomatic households: where the defendant is a diplomat, apply Reyes and Basfar; consider state immunity (see Benkharbouche v Secretary of State for Foreign and Commonwealth Affairs [2017] UKSC 62).
Client care and expectation management: explain the threshold; warn of the credibility risk; comply with SRA Principle 7 and paragraph 3.4 of the Code of Conduct on competence.

Risk Flags

Limitation is unforgiving in employment claims.
Sponsor reporting duties may lead to curtailment before SW 18.3 can be invoked.
The public order disqualification under section 63 of the Nationality and Borders Act 2022, as strengthened by section 29 of the Illegal Migration Act 2023 (which survives the 2025 repeals), may exclude otherwise qualifying victims and must be screened in every case.
Data protection issues arise in NRM referrals; the client must be advised of the safeguarding pathway.
Pure wage claims or contractual claims framed as modern slavery risk negative CG decisions that contaminate future immigration applications on credibility, and expose the solicitor to a professional conduct concern under SRA Principles 2 and 7 and paragraph 3.4 of the Code.

Conclusion

The correct position is that modern slavery for the purposes of SW 18.3 relief means what the Modern Slavery Act 2015, the Coroners and Justice Act 2009 and Article 4 ECHR say it means, as clarified by the Supreme Court in Reyes and Basfar. Non-payment of wages, unpaid holiday and contractual exploitation are not enough on their own. Home Office concessions will not fill the gap. The correct advice for a client whose grievance is limited to those matters is to pursue the Employment Tribunal, HMRC National Minimum Wage enforcement and other labour law remedies, and to reserve the NRM for cases in which the coercive, deceptive and vulnerability-abusing features of modern slavery are genuinely present.

Authoritative Sources

Benkharbouche v Secretary of State for Foreign and Commonwealth Affairs [2017] UKSC 62: https://www.bailii.org/uk/cases/UKSC/2017/62.html

MS (Pakistan) v SSHD [2020] UKSC 9: https://www.bailii.org/uk/cases/UKSC/2020/9.html

R (MN and IXU) v SSHD [2020] EWCA Civ 1746: https://www.bailii.org/ew/cases/EWCA/Civ/2020/1746.html

R v SK [2011] EWCA Crim 1691: https://www.bailii.org/ew/cases/EWCA/Crim/2011/1691.html

Hounga v Allen [2014] UKSC 47: https://www.bailii.org/uk/cases/UKSC/2014/47.html

Siliadin v France (2006) 43 EHRR 16: https://hudoc.echr.coe.int/eng?i=001-72091

CN v United Kingdom (2013) 56 EHRR 24: https://hudoc.echr.coe.int/eng?i=001-122874

Chowdury v Greece (App no 21884/15): https://hudoc.echr.coe.int/eng?i=001-172701

Van der Mussele v Belgium (1983) 6 EHRR 163: https://hudoc.echr.coe.int/eng?i=001-57591

Support Bodies

Gangmasters and Labour Abuse Authority: https://www.gla.gov.uk/

ACAS: https://www.acas.org.uk

The Salvation Army Modern Slavery Referral Helpline: https://www.salvationarmy.org.uk/modern-slavery

Migrant Help: https://www.migranthelpuk.org/

Kalayaan (support for migrant domestic workers): https://www.kalayaan.org.uk/

Unseen: https://www.unseenuk.org/

Author: Jawad Bhatti, LLB (Hons), LPC, LLM, MBA — Solicitor of England & Wales, Morgan Hill Solicitors.

Disclaimer: This article is provided for general information only and does not constitute legal advice on any specific case. The law stated is as at 12 September 2026 and includes provisions of Statement of Changes HC 584 which come into force on 8 October 2026. If you require advice on a Skilled Worker, modern slavery or employment matter, please contact Morgan Hill Solicitors.