Civil Penalty for Illegal Working: How the UK Penalty Calculation Actually Works

The Home Office does not start every illegal-working penalty at £45,000. They start at a lower figure and add to it. Or they start at the maximum and reduce it. Or they replace the civil-penalty route entirely with criminal proceedings. Which path your business is on depends on a small number of facts the case-worker decides early in the investigation.

This guide walks through how a civil penalty for illegal working is actually calculated under the current Home Office Code of Practice, so the figure you see in a notice is not a surprise.

This guide is for informational purposes only and does not constitute legal advice. For advice on your specific situation, consult a qualified immigration solicitor.

What the civil penalty is

A civil penalty for illegal working is a financial sanction issued by the Home Office under Section 15 of the Immigration, Asylum and Nationality Act 2006. It applies when an employer employs a person who:

• Is subject to immigration control, and
• Has not been granted permission to work or is in breach of the conditions of their permission, and
• The employer cannot show a statutory excuse — i.e. they did not carry out a compliant right to work check at the prescribed times.

The penalty is per illegal worker, not per business. Employ three people without a statutory excuse and three separate penalties are calculated.

The maximum civil penalty rates (as of 13 February 2024) are:

Offence	Maximum per worker
First breach	£45,000
Repeat breach (within 3 years of a previous penalty)	£60,000

These rates are confirmed on the Home Office penalties for employing illegal workers page and tripled the previous maximums (£15,000 / £20,000) when introduced.

But the headline maximum is rarely the actual penalty issued. The case-worker applies a starting figure based on the offence type and then adjusts it based on mitigating and aggravating factors set out in the Code of Practice on Preventing Illegal Working (13 February 2024).

How the calculation works in practice

The case-worker progresses through a structured calculation. The exact mechanics are in the Code of Practice, but the steps are:

1. Identify the offence type

• First breach: the employer has not previously been issued with a civil penalty for illegal working in the last three years.
• Repeat breach: there has been at least one prior penalty within three years.

2. Apply the relevant starting figure

The Code of Practice sets the starting amounts for each offence type. The maximum for first breach is £45,000 per worker; for repeat breach, £60,000.

3. Apply mitigating factors (reductions)

Each mitigating factor that applies reduces the per-worker penalty by a specified amount:

• Reporting suspicions before the Home Office contacts you (with a Unique Reference Number): if the employer voluntarily reported a suspected illegal worker to the Home Office and received a Unique Reference Number before any enforcement action, a £5,000-per-worker reduction applies.
• Active co-operation with the investigation: evidence of co-operation during a Home Office visit and investigation reduces the penalty by £5,000 per worker.
• Effective right-to-work checking practices alongside mitigation factors 1 and 2: evidence that effective check processes were in place can result in a Warning Notice rather than a Civil Penalty Notice for a first breach.

4. Apply aggravating factors (increases)

The Code of Practice also identifies aggravating factors, including:

• The employer has been issued with a previous warning notice or referral notice.
• The illegal working was widespread or systematic across the workforce.
• Non-cooperation during the investigation.

5. Apply the fast-payment discount (if eligible)

If the (potentially adjusted) penalty is paid within 21 days of the notice, a 30% fast-payment discount is applied. This is on top of any mitigating-factor reductions, but only available if the employer also accepts the penalty (does not object or appeal).

6. Multiply by the number of illegal workers

The final per-worker figure is multiplied by the number of workers identified.

So a small employer with 2 workers identified, no prior penalties, partial cooperation, and prompt payment would see a fundamentally different bill from an employer with 3 workers, a prior warning, and an appeal that loses.

A worked example for a micro-employer

A 6-person catering business is investigated. Two visa-holding employees are identified as not having had compliant follow-up checks. Their visas expired 4 months ago. The employer has no prior penalties.

Step 1: First breach. Step 2: Starting figure £45,000 per worker = £90,000 total maximum. Step 3: Mitigating factors — the employer cooperated promptly and had documented initial checks for both employees. One mitigation tier applied; for illustration assume a reduction of £5,000 per worker. Step 4: No aggravating factors. Step 5: Adjusted per-worker = £40,000. Two workers = £80,000. Step 6: If paid within 21 days and not contested, 30% fast-payment discount = £56,000 final liability.

The numbers above are illustrative — actual reductions and increases depend on the specific facts and the case-worker's assessment. They show the range: the same set of facts can produce a five-figure liability or a six-figure one, depending on cooperation, prior history, and payment timing.

For your specific business and headcount, the penalty risk calculator walks through the same calculation against your numbers.

When civil penalty becomes criminal prosecution

The civil penalty regime applies where the employer could not show a statutory excuse — typically a missed check or missed follow-up. It is fundamentally a strict-liability process: the question is whether a compliant check happened at the right time, not whether the employer "knew".

A separate criminal offence applies where the employer knowingly employed someone without the right to work, or had reasonable cause to believe they did not. Under Section 21 of the Immigration, Asylum and Nationality Act 2006 (as amended by the Immigration Act 2016), the maximum on conviction on indictment is:

• 5 years' imprisonment, and
• An unlimited fine

The threshold for criminal prosecution is "knew or had reasonable cause to believe". An employer who continued employing a worker after their visa had visibly expired, or who employed someone with a document they had reason to believe was false, can be prosecuted rather than (or in addition to) being issued a civil penalty.

For most small UK employers the civil-penalty route is the likely outcome of an investigation. The criminal route comes into play in cases involving deliberate non-compliance or document fraud.

Notice, objection, and appeal

When a civil penalty is issued, the employer receives a Civil Penalty Notice setting out:

• The names of the workers identified
• The per-worker penalty figures and reasoning
• Any mitigating or aggravating factors applied
• The total liability
• The fast-payment date for the 30% discount

The employer has 28 days to:

1. Pay (with the 30% discount if paid within 21 days), or
2. Object to the Home Office (an internal review), or
3. Pay the full amount over an agreed instalment plan.

If the objection is rejected, the employer can appeal to the County Court within 28 days of the objection outcome. Appeals are heard on the merits and look afresh at whether the statutory excuse defence applies.

Critically: choosing to object or appeal forfeits the 30% fast-payment discount even if the appeal eventually succeeds in part. So the early-stage decision to contest is a real financial trade-off, and not one to make without advice from a specialist immigration solicitor.

How to avoid the calculation entirely

The most reliable way to avoid every step in the calculation above is to maintain the statutory excuse for every employee, every time. That means:

1. Run a compliant initial check for every hire, including British citizens. Selective checking is unlawful discrimination under the Equality Act 2010 and undermines your statutory-excuse position. See our British citizens guide.
2. Identify the document list and group correctly. List A is the easy case (no follow-up). List B Group 1 and Group 2 carry different follow-up cycles — see the right to work documents list.
3. Track every visa expiry date and Group 2 follow-up date. Our visa expiry tracking guide walks through the practical setup.
4. Run the follow-up check before, not after, expiry. Follow-up right to work checks covers the mechanics.
5. Use the 28-day grace period correctly — it is not an extension you grant yourself; it is a verification window in specific circumstances.
6. Document everything with dates and copies. A complete, dated audit trail is the single best evidence in an investigation.

A statutory excuse is binary — you either have it or you do not. Once you do, the civil-penalty calculation never starts. That is the calculation worth making.

Sources

• Code of Practice on Preventing Illegal Working (13 February 2024) — GOV.UK
• Penalties for employing illegal workers — GOV.UK
• Illegal working civil penalties: an employer's guide — GOV.UK
• Immigration, Asylum and Nationality Act 2006, Section 15 — legislation.gov.uk
• Immigration, Asylum and Nationality Act 2006, Section 21 — legislation.gov.uk