If you run a recruitment agency in the UK, the off-payroll working rules (commonly called IR35) are probably the single biggest compliance risk you face. HMRC has been targeting recruitment agencies specifically for several years now, and the rules have only got tighter since the reforms were extended to the private sector in April 2021.

This is not about whether your contractors like being inside or outside IR35. It is about whether you, as the recruitment agency, have followed the correct legal process for determining their status. Get that wrong, and you could be liable for unpaid tax, National Insurance, and penalties going back years.

Let me walk through exactly what the off-payroll working rules mean for your recruitment agency, and give you a practical compliance checklist you can use today.

What Are the Off-Payroll Working Rules?

The off-payroll working rules are designed to identify workers who would be employees if they were engaged directly, but who currently work through an intermediary (typically their own limited company). HMRC calls these "deemed employees." The rules shift the responsibility for determining employment status from the worker to the organisation that receives their services.

For recruitment agencies, this matters because you are often the "fee-payer", the entity that pays the contractor's limited company. That makes you responsible for operating PAYE and National Insurance on the deemed employment income if the contractor is found to be inside IR35.

The rules apply where:

  • The worker provides services through an intermediary (usually their own limited company)
  • The client is a medium or large organisation (the vast majority of businesses you work with)
  • The worker would be an employee of the client if engaged directly

If all three conditions are met, the client must issue a Status Determination Statement (SDS) before the engagement starts. The recruitment agency then becomes responsible for operating payroll taxes on the fees paid to the contractor's company.

Why Recruitment Agencies Are the Prime Target

HMRC knows that recruitment agencies sit in the middle of the chain. You take the fee from the client, deduct your margin, and pay the contractor's limited company. If the contractor is inside IR35, HMRC expects tax and NI to be deducted at source, just like a normal employee.

The problem is that many recruitment agencies have historically treated all contractors as outside IR35, relying on blanket determinations or simply not asking the right questions. HMRC has been issuing "nudge letters" to recruitment agencies since 2022, and we are now seeing full compliance reviews and tax bills running into six figures.

As ICAEW qualified accountants, we have seen cases where a recruitment agency with 30 contractors on its books received a retrospective bill for £340,000 in unpaid tax and penalties. That is the kind of liability that can put an agency out of business.

Your Responsibilities as a Recruitment Agency

Under the off-payroll working rules, the recruitment agency's responsibilities depend on where you sit in the contractual chain. In most cases, you are the fee-payer. That means:

  • Receiving the SDS: The client must give you a Status Determination Statement before the contractor starts work. You must pass this on to the contractor.
  • Operating PAYE: If the SDS says the contractor is inside IR35, you must deduct income tax and employee NI from the payments you make to the contractor's limited company. You also pay employer NI at 13.8%.
  • Reporting to HMRC: You report these deductions through your regular RTI (Real Time Information) submissions, just like you do for permanent employees.
  • Appealing the SDS: If the client's SDS says the contractor is outside IR35 but you disagree, you can challenge it. However, you must have reasonable grounds for doing so.

If you are a smaller agency acting as an employment business, you may also have responsibilities under the Conduct of Employment Agencies and Employment Businesses Regulations 2003. Those are separate from IR35, but they add another layer of compliance.

What Happens If the Client Gets It Wrong?

This is where it gets complicated. If the client issues an SDS saying the contractor is outside IR35, but HMRC later determines that the contractor was actually inside the rules, the liability for unpaid tax usually falls on the fee-payer, which is you, the recruitment agency.

There is a due diligence defence available, but it is narrow. You must be able to show that you took reasonable care when reviewing the client's SDS, and that you had no reason to believe the determination was wrong. In practice, that means you need to understand the client's working practices, not just accept their word.

The SDS: What You Need to See

A valid Status Determination Statement must include:

  • The client's name and address
  • The worker's name and the intermediary's details
  • A clear statement of whether the worker is inside or outside IR35
  • The reasons for that determination (not just a tick box)
  • The date the determination was made
  • The client's signature (or electronic equivalent)

If the client sends you a one-line email saying "John is outside IR35," that is not a valid SDS. You should push back and ask for a proper determination. HMRC will not accept a flimsy document if they come knocking.

Practical Compliance Checklist for Recruitment Agencies

Here is a checklist you can use today. Work through it with your compliance team or your accountant.

Before You Place a Contractor

  • Confirm the client is a medium or large organisation (check Companies House if unsure)
  • Request a completed SDS from the client before the contractor starts
  • Review the SDS for completeness, does it include reasons, not just a conclusion?
  • If the SDS says "outside IR35," do you have reasonable grounds to agree?
  • Send the SDS to the contractor within the required timeframe (before the first payment)
  • Document your review process, keep a record of what you checked and why

During the Engagement

  • If the SDS says "inside IR35," set up the contractor on your payroll system
  • Deduct income tax and NI from each payment to the contractor's limited company
  • Report through RTI on or before the payment date
  • Pay employer NI at 13.8% on the deemed employment payment
  • Issue a payslip to the contractor for each payment
  • If the working practices change during the engagement, ask the client for a new SDS

Ongoing Compliance

  • Keep all SDS documents for at least 6 years after the engagement ends
  • Review your contractor population quarterly, are there any changes in working patterns?
  • Train your recruitment consultants on IR35 basics, they are the ones having the conversations
  • Consider using IR35 assessment tools for your own due diligence (but remember the CEST tool is directional only)
  • Speak to your accountant if you are unsure about any determination

Common Mistakes Recruitment Agencies Make

I see the same errors repeatedly. Here are the ones that cause the most damage.

Blanket determinations. Some agencies accept blanket "outside IR35" statements from clients without question. That is not due diligence. If HMRC investigates, they will want to see evidence that you considered each contractor's specific circumstances.

Not passing the SDS to the contractor. The rules require you to pass the SDS to the contractor. If you do not, you are in breach. It also creates a paper trail problem if HMRC asks to see it.

Ignoring the fee-payer status. Even if the client is the one making the determination, you are the one who pays the tax if it goes wrong. Treat every SDS as a potential liability until you have satisfied yourself it is correct.

Assuming umbrella companies solve the problem. Umbrella companies can help with payroll administration, but they do not remove your IR35 obligations. You still need to ensure the correct determination has been made.

What If HMRC Investigates?

If HMRC opens a compliance check on your agency, they will typically ask for:

  • A list of all contractors you have placed in the last 3-6 years
  • Copies of all SDS documents
  • Evidence of your due diligence process
  • Payroll records for contractors deemed inside IR35
  • Correspondence with clients about IR35 determinations

If you have followed the checklist above, you should be able to produce everything they ask for within a few days. If you cannot, that is a red flag. HMRC will assume the worst and start calculating what you owe.

The penalty regime for non-compliance is serious. You can face penalties of up to 100% of the tax due for deliberate non-compliance, plus interest going back to the original due date. For a recruitment agency with a large contractor book, that can easily reach hundreds of thousands of pounds.

Working With Your Accountant on IR35

This is not something you should handle alone. Your accountant should be involved in:

  • Reviewing your contractor contracts and engagement models
  • Advising on the correct payroll treatment for inside-IR35 contractors
  • Helping you document your due diligence process
  • Representing you if HMRC opens a compliance check
  • Advising on the tax implications of different fee structures

At Agency Founder Finance, we work with recruitment agencies across the UK to get their IR35 compliance right. If you are unsure whether your current processes are adequate, get in touch. We can review your contractor book and tell you where the risks are.

We also work with recruitment agencies specifically to structure their contractor engagements properly from the start. Prevention is cheaper than a retrospective HMRC bill.

Final Thoughts

The off-payroll working rules are not going away. If anything, HMRC is likely to increase its focus on recruitment agencies in the coming years. The compliance burden is real, but it is manageable if you have the right processes in place.

Start with the checklist above. If you cannot tick every box for your current contractor placements, you have work to do. Your accountant can help you get there.

And if you are reading this thinking "we have never had an SDS from any of our clients," that is your starting point. Call your clients tomorrow and ask for them. It is better to fix this now than to explain it to an HMRC inspector later.