In 2023, the owner of a chain of car washes across the East Midlands was sentenced to two years' imprisonment. He had employed 26 people without the right to work in the UK. His defence was that he did not know their immigration status — he had never asked, never checked, and considered it none of his business. The court was unpersuaded. The duty to prevent illegal working is not contingent on the employer's curiosity. It exists whether the employer engages with it or not.
This case sits at the extreme end of enforcement. But the legal duty it rests on — the obligation on every UK employer to take reasonable steps to prevent illegal working — applies to every business, from the car wash to the corporate headquarters. It applies to the fish and chip shop with three employees and the NHS trust with thirty thousand. The scale differs. The duty does not.
Understanding this duty — where it comes from, what it requires, and how it interacts with discrimination law — is foundational to compliant employment in the UK.
The statutory framework
The employer's duty to prevent illegal working is established primarily by Section 15 of the Immigration, Asylum and Nationality Act 2006 (the "2006 Act"). This section creates a civil penalty regime: employers who employ someone who does not have the right to work in the UK are liable to a penalty of up to £60,000 per illegal worker.
The 2006 Act was supplemented by the Immigration Act 2014 and the Immigration Act 2016, which strengthened enforcement powers, increased penalties, and introduced criminal offences for employers who knowingly employ illegal workers.
The current framework, as set out in Home Office guidance on illegal working penalties, creates a two-tier liability system:
Civil liability (Section 15, 2006 Act)
An employer is liable to a civil penalty if they employ a person who does not have the right to work in the UK and they have not established a statutory excuse by conducting a compliant right-to-work check. The penalty is strict: it does not require the employer to have known about the worker's immigration status. The fact of employment without a valid check is sufficient.
The penalty levels are:
- Up to £45,000 per illegal worker for a first offence
- Up to £60,000 per illegal worker for repeat offences
The statutory excuse — established by conducting the prescribed three-step right-to-work check — provides a complete defence against civil penalties. If the employer can demonstrate they followed the prescribed check process, they are not liable, even if the worker's documents were fraudulent or their immigration status was misrepresented.
Criminal liability (Section 21, 2006 Act, as amended)
An employer commits a criminal offence if they employ a person who they know or have reasonable cause to believe does not have the right to work in the UK. This is a higher threshold than the civil penalty: it requires knowledge or constructive knowledge, not just the absence of a check.
The penalties for the criminal offence are severe:
- An unlimited fine
- Up to 5 years' imprisonment
The distinction between "knowing" and "having reasonable cause to believe" is critical. An employer who receives a tip-off that a worker's documents are forged and ignores it has "reasonable cause to believe." An employer who notices that a worker's visa has expired and takes no action has "reasonable cause to believe." The threshold is not wilful blindness — it is any circumstance that would put a reasonable person on notice.
What "prevent" actually means in practice
The duty to prevent illegal working is not a duty to guarantee that no illegal worker will ever be employed. That would be impossible, given the sophistication of modern document fraud and the limitations of the information available to employers. The duty is to take reasonable steps — specifically, to conduct the prescribed right-to-work checks as set out in the Home Office employer guidance.
In practice, this means:
Check before employment begins
The prescribed right-to-work check must be completed before the person starts work. This applies to all employees, regardless of nationality, appearance, or the employer's perception of their immigration status. The check must follow the three-step process: obtain original documents from the prescribed list, check them in the presence of the holder, and retain dated copies.
Check everyone equally
The duty to prevent illegal working must be balanced against the prohibition on discrimination. The Equality Act 2010 prohibits discrimination on the grounds of race, which includes nationality and ethnic origin. An employer who checks the right-to-work status of some employees but not others — based on their appearance, accent, name, or perceived nationality — is discriminating.
The Home Office guidance is explicit on this point: the right-to-work check must be conducted for every employee, using the same process. The employer should not make assumptions about who does or does not need checking. A British citizen is subject to the same process as a visa holder. The only way to avoid discriminatory application is to apply the process universally.
This creates an important practical implication. An employer who says "we only check people who look like they might be foreign" is not only failing their duty to prevent illegal working — they are also committing an offence under discrimination law. Universal application is both the compliant and the lawful approach.
Conduct follow-up checks for time-limited permissions
The duty does not end with the initial check. For employees with time-limited right to work, the employer must conduct follow-up checks before the permission expires. Failure to do so means the statutory excuse lapses at the expiry date, and the employer is exposed to civil penalties from that point onwards.
This is a particular challenge for employers with large workforces or high proportions of visa holders. Tracking visa expiry dates across dozens or hundreds of employees requires a systematic approach — diary reminders at minimum, automated alert systems ideally.
Respond to information received
If an employer receives information suggesting that a worker does not have the right to work — from the Home Office, from a colleague, from the worker themselves — they have a duty to act on it. This does not mean immediately dismissing the worker (which could itself be unlawful). It means conducting a fresh verification check to establish the worker's current status.
Ignoring credible information is the fastest route from civil liability to criminal liability. The threshold for "reasonable cause to believe" is not certainty — it is any information that a reasonable employer would treat as warranting investigation.
The ignorance trap
The most dangerous misconception about the duty to prevent illegal working is that ignorance provides protection. "I didn't know" is not a defence against civil penalties. The civil penalty regime is strict liability, subject only to the statutory excuse. If you employed someone without the right to work and did not conduct a compliant check, you are liable. Your knowledge or lack of knowledge about the worker's status is irrelevant.
For the criminal offence, ignorance is relevant — but only if it is genuine. Wilful ignorance, deliberate avoidance of information, or failure to respond to red flags will be treated as "reasonable cause to believe." An employer who structures their business to avoid learning about workers' immigration status — by, for example, outsourcing hiring to an agent with instructions not to ask — will not be protected.
The case law on this point is clear: the duty to prevent illegal working is an active duty. It requires the employer to take positive steps — to check, to verify, to record, to follow up. Passivity is not compliance.
Repeat offender escalation
The penalty framework includes escalation for repeat offences. An employer who receives a civil penalty and subsequently employs another illegal worker faces higher penalties (up to £60,000 per worker compared to £45,000 for a first offence) and is more likely to face criminal prosecution.
Additionally, a history of civil penalties is a factor in sentencing for criminal offences. An employer who has received multiple penalty notices and continues to employ people without conducting checks will find it very difficult to argue that they did not have "reasonable cause to believe."
For businesses that hold a sponsor licence, the consequences extend further. A civil penalty for illegal working is grounds for sponsor licence revocation. Losing a sponsor licence means every sponsored worker in the organisation must stop working, often within a 60-day curtailment period. For businesses heavily reliant on sponsored workers — in health and social care, hospitality, and technology — this can be operationally catastrophic.
How the duty interacts with the Fair Work Agency
The Fair Work Agency, launching in April 2026, consolidates the enforcement bodies responsible for employment standards, minimum wage, labour abuse, and — critically — illegal working. The FWA's integrated intelligence approach means that a failure identified in one domain can trigger investigation across all domains.
A minimum wage complaint that leads to an FWA visit could result in right-to-work checks being demanded. An employment agency standards inspection could uncover immigration compliance failures. The silos that previously allowed employers to manage each compliance obligation separately are being dismantled.
For employers, this means the duty to prevent illegal working can no longer be treated in isolation. It sits within a broader compliance landscape that includes employment rights, health and safety, and tax obligations. The FWA is designed to assess all of these simultaneously.
Building a compliant system
The duty to prevent illegal working is met by doing three things consistently:
- Check every employee before they start, using the prescribed process, regardless of nationality
- Track and re-check time-limited permissions before they expire
- Maintain records — dated copies, audit trails, and evidence of follow-up — that demonstrate compliance at any point in time
For businesses without dedicated compliance teams, maintaining this consistency is the challenge. A single missed check, a single expired visa that goes unnoticed, a single record that cannot be located — any of these can eliminate the statutory excuse and create liability.
Certifyd's Right to Work Portal automates the prescribed check process, creating a statutory excuse from the moment verification is completed. Every check is timestamped, every document is retained, and every time-limited permission is tracked with proactive alerts. The system applies the same process to every employee — eliminating the risk of discriminatory application — and produces an audit trail that satisfies both the Home Office and the Fair Work Agency.
For employers who want to meet their duty to prevent illegal working without building a compliance department, find out how Certifyd works.