Private-sector IR35 matters when an architecture contractor works through an intermediary, such as a personal service company, and the assignment needs to be assessed for tax status.
This is not tax advice. Use the GOV.UK off-payroll working collection, the relevant contractor guidance and specialist advice before making decisions.
The first question is client size
For contractors, the private-sector rules depend heavily on who the client is. If the client is small and outside the public sector, the worker’s intermediary usually remains responsible for deciding employment status for tax.
If the client is medium or large, the client is generally responsible for deciding the worker’s employment status for tax and operating the off-payroll rules through the chain.
- Read GOV.UK guidance for contractors working with small private-sector clients.
- Read GOV.UK guidance for contractors working with public-sector or medium and large clients.
- Clients can use the Check Employment Status for Tax tool as part of the assessment.
Listen: business risk and architecture practice
This Architecture Social episode adds a broader business conversation about risk, reward and commercial judgement in architecture.
What contractors should ask before accepting
- Is the client small, medium or large for off-payroll purposes?
- Who is making the status decision?
- Will I receive a Status Determination Statement and reasons?
- Is the assignment inside or outside IR35?
- Who is the fee payer?
- Is payment through payroll, an umbrella company, an agency or my limited company?
- What are the actual working practices day to day?
Working practices matter more than labels
A contract can say consultant, contractor or project support, but the day-to-day reality still matters. If the client controls hours, tasks, supervision and integration like a permanent employee, the risk profile changes.
Architecture roles can be particularly messy because project pressure can pull a contractor into staff-style work quickly. If the assignment starts as a defined package but becomes ongoing cover, the status position may need to be reconsidered.
Architecture examples to test the working reality
The same job title can describe very different assignments. A contractor brought in to deliver a defined Revit package with their own method, clear outputs and limited supervision is not the same as someone filling a permanent team gap five days a week under direct management.
- Is the contractor judged on output or attendance?
- Can they decide how the work is done?
- Are they using their own business judgement or following staff instructions?
- Is substitution genuinely possible in the context of the project?
- Would the client treat a permanent employee in the same way?
When the determination feels wrong
GOV.UK guidance says workers can dispute a status determination. The client has to consider the reasons and respond, but the safest move is to raise concerns early rather than after the first invoice has already gone through.
- Keep a copy of the SDS.
- Write down why you disagree.
- Ask how the client reached the decision.
- Check whether the working practices match the contract.
- Take specialist advice if the risk is material.
Rate and route need to be clear
Inside-IR35 and outside-IR35 assignments are not the same commercial offer. The tax handling, employer costs, umbrella route, expenses and take-home pay can all change the value of the role.
That does not mean every inside-IR35 role is bad. It means the project, rate, duration and payment route have to be transparent enough for the contractor to decide properly.
Small client confirmation is worth getting
If the client says it is small and therefore the intermediary remains responsible for status, ask for confirmation. Do not rely on a casual comment from the hiring manager if the tax route changes the risk.
For recruiters and agencies, this is also a trust issue. Contractors make better decisions when the size test, status route and payment chain are explained before interview or offer stage.
Common mistakes
- Assuming every private-sector client has the same responsibility.
- Accepting the assignment before seeing the status position.
- Only checking the contract and ignoring working practices.
- Confusing umbrella employment with outside-IR35 contracting.
- Treating a high day rate as enough compensation for unclear risk.
Architecture Social view
Stephen’s recruiter view is that contractors should protect their time and their risk. A great project can still be the wrong move if the status, rate and working reality are vague.
Next step
Before accepting a private-sector architecture contract, ask for the status decision, payment route and working practices in writing. For related reading, see the umbrella company guide and the off-payroll working guide for architecture contractors.
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