HMRC NI Compliance Checks

Key facts

HMRC conducts PAYE audits that include checking employer NI contributions.
A common focus is employment status — whether workers classified as self-employed should actually be employees (with employer NI due).
Penalties for incorrect NI treatment can include the NI underpaid plus interest, and in serious cases additional penalties of up to 100%.
Employers have the right to be represented by an accountant or tax adviser during a compliance check.
HMRC will usually write to you first — you typically have 30 days to respond or provide records.

What Is an NI Compliance Check?

An NI compliance check is an investigation by HMRC into whether an employer is correctly calculating, reporting, and paying National Insurance contributions. These checks are usually conducted as part of a broader PAYE compliance review but can also focus specifically on NI issues.^[1]

HMRC has the legal power to:

Inspect employer records and payroll data
Visit business premises
Interview directors and payroll staff
Request information from third parties (banks, workers, etc.)
Assess additional NI due, plus interest and penalties

Common Triggers for an NI Compliance Check

HMRC uses risk-based selection to decide which employers to check. Common triggers include:^[1]

Trigger	What HMRC Is Looking For
RTI discrepancies	Differences between RTI submissions and other data (SA returns, bank records)
Low NI relative to workforce	An employer with many workers but low NI payments — suggests workers may be misclassified
CIS subcontractor usage	Construction firms using large numbers of “self-employed” workers
Off-payroll working (IR35)	Engaging workers through personal service companies
Worker complaints	A worker contacts HMRC claiming they should be an employee
Benefits in kind	No or low P11D submissions despite company cars, medical insurance, etc.
Random selection	Routine audit as part of HMRC’s compliance programme

Employment Status Reviews

One of the most significant areas of NI compliance is employment status. HMRC checks whether workers classified as self-employed (and therefore not subject to employer’s NI) should actually be treated as employees.^[2]

If HMRC determines that a worker is an employee rather than self-employed, the employer becomes liable for:

Employer’s NI (15% on earnings above the Secondary Threshold) — for the entire period of misclassification
Employee’s NI (8%/2%) — the employer may have to bear this cost if it cannot be recovered from the worker
Interest on the underpaid NI
Penalties if the misclassification was careless or deliberate

The cost of reclassification can be substantial. For a worker earning £40,000 per year incorrectly classified as self-employed, the employer could owe approximately £4,635 per year in employer’s NI alone (15% on £30,900). Over three years, that’s nearly £14,000 before interest and penalties.^[2]

What Happens During a Compliance Check

A typical NI compliance check follows these stages:^[1]

Stage 1: Notification

HMRC writes to the employer (or their agent) explaining that a compliance check is being opened. The letter will:

State which tax periods are being checked
List the records HMRC wants to see
Set a deadline (usually 30 days) to provide the information
Name the HMRC officer handling the case

Stage 2: Information Gathering

HMRC reviews the records provided. They may request additional information, visit business premises, or interview staff. Common records requested include:

Payroll records and RTI submissions
Employment contracts and worker agreements
Invoices from self-employed workers
P11D returns (benefits in kind)
Evidence of how employment status was determined

Stage 3: Findings

HMRC writes to the employer with their findings. This may include:

Confirmation that everything is correct (no further action)
Identification of errors with a calculation of underpaid NI
A proposed penalty (if applicable)
An opportunity to make representations before a final decision

Stage 4: Settlement or Appeal

The employer can accept the findings and pay any additional NI due, or dispute the findings and request a review or appeal.

Penalties for NI Errors

Penalties for incorrect NI are based on the type of error:^[3]

Type of Error	Penalty Range
Reasonable care taken (genuine mistake)	0% — no penalty
Careless (lack of reasonable care)	0%–30% of underpaid NI
Deliberate (intentional error)	20%–70% of underpaid NI
Deliberate and concealed	30%–100% of underpaid NI

Penalties are reduced if the employer makes an unprompted disclosure (tells HMRC before they discover the error) rather than a prompted disclosure (only admits after HMRC finds it). Cooperation during the investigation also reduces penalties.

How to Respond to a Compliance Check

If you receive notice of an NI compliance check:^[1]

Don’t panic — many checks result in no additional liability
Notify your accountant or tax adviser immediately — they can liaise with HMRC on your behalf
Gather the requested records within the deadline
Be cooperative — this can reduce any penalties if errors are found
Don’t destroy records — this could be treated as obstruction
Respond within the deadline — if you need more time, contact HMRC to request an extension

Professional representation: You have the right to be represented by an accountant, tax adviser, or solicitor at all stages of a compliance check. Their fees may be covered by your professional indemnity or tax investigation insurance, if you have it.

Appealing a Decision

If you disagree with HMRC’s compliance check findings:^[4]

Request a review — a different HMRC officer will review the decision (free and usually faster)
Appeal to the First-tier Tribunal — an independent tax tribunal that hears appeals. You must appeal within 30 days of the decision
Upper Tribunal — if you disagree with the First-tier Tribunal’s decision, you can appeal on a point of law

Frequently Asked Questions

What triggers an HMRC NI compliance check?

Common triggers include discrepancies in RTI submissions, patterns of low NI payments relative to workforce size, use of off-payroll workers, CIS arrangements, complaints from workers, and random selection for routine audit.

What records will HMRC want to see?

HMRC may request payroll records, RTI submissions, employment contracts, worker invoices, P60s and P45s, benefits-in-kind records (P11D), and evidence of employment status determinations for off-payroll workers.

What are the penalties for incorrect employer NI?

If HMRC finds that employer NI was underpaid, you must pay the shortfall plus interest. Additional penalties range from 0% (unprompted disclosure, reasonable care taken) to 100% of the underpaid NI for deliberate and concealed errors.

Can I appeal against an HMRC NI compliance decision?

Yes. If you disagree with HMRC’s findings, you can request a formal review by a different HMRC officer. If you’re still not satisfied, you can appeal to the First-tier Tribunal (Tax Chamber) within 30 days.

Sources

HMRC compliance checks — GOV.UK
Employment status — GOV.UK
HMRC penalties for errors — GOV.UK
Tax appeals — GOV.UK