Your IR35 status determination is, in the first instance, a tax decision — and usually not one you make yourself. Since the off-payroll reforms, for medium and large clients it is the end client who decides whether your engagement is inside or outside IR35, issuing a Status Determination Statement. That decision then flows straight through to how you are paid, and from there to how much you can borrow. This article explains the connection, and — importantly — which parts of it you can still control when it comes to your mortgage.
Principles here are stable; exact lender figures are confirmed at application, and IR35 status itself is a tax matter for you and your accountant, not mortgage advice.
Who decides your status
For engagements with medium and large end clients, the client is responsible for determining your IR35 status and must provide a Status Determination Statement setting out the decision and its reasoning. For small clients, the responsibility generally remains with your own limited company. Either way, the determination sets whether your income is taxed as employment (inside) or invoiced gross by your company (outside) — and that split is the starting point for how a mortgage lender sees you.
How the determination flows into your borrowing
Inside IR35, tax and National Insurance are deducted at source, so your take-home is lower. Outside IR35, your company invoices the full contract value and you manage your own tax. The determination therefore shapes the raw material a lender works with. But — and this is the crucial point — it does not fix your borrowing. Whether you are assessed on the gross contract value or on your take-home is decided by the lender, not by the determination. Two inside-IR35 contractors on identical determinations can borrow amounts more than £200,000 apart, purely on which lender assesses the application.
So the determination is a tax fact you often cannot control; the lender who reads it is entirely within your control. That is where the mortgage outcome is actually decided.
What you can control
Three things, all of them within your gift:
- Which lender receives the application.Inside IR35, target a lender that assesses the gross contract value; outside IR35, a lender that assesses the day rate rather than your drawings. This single choice moves the number most.
- How the income is evidenced.Lead with the contract, an agency rate confirmation, or — for umbrella — the Key Information Document, so the gross rate is what the underwriter sees. Payslips alone undersell an inside or umbrella position.
- The timing.If a determination or contract is about to change, the timing of your application relative to that change can matter, because lenders assess your position at application and again at offer.
Worked example
Illustrative only, showing why the lender matters more than the determination. Take an inside-IR35 contractor on £550 a day:
- Assessed on gross contract value:550 x 5 x 46 = £126,500 → around £569,000 at 4.5x.
- Assessed on net take-home(roughly £80,000 after deductions): around £360,000.
- Same determination, same contract — over £200,000 apart, decided by the lender.
Where to take care
If your status determination changes during a live application — a contract renewed on different terms, a client reassessing — tell your adviser immediately, because lenders reassess up to offer and an undisclosed change can unravel a case late. Handled openly, a change is manageable; hidden, it is a risk. The determination is your client’s to make, but keeping the mortgage application aligned with your current position is yours to manage.