IR35 determines how lenders read your contract income — the same £600-a-day contractor can be assessed as earning £138,000 or £85,000 depending on the lender and arrangement. This 2026 guide covers what your status means for assessment, how inside, outside and umbrella contracts are documented, and how to choose lenders that protect your borrowing power — with dedicated pages linked for each arrangement.
IR35 (the off-payroll working rules) tests whether a contractor working through an intermediary — usually their own limited company — would be an employee if engaged directly. Outside IR35 means genuine self-employment: your company invoices gross, and you manage your own tax. Inside IR35 means employment-equivalent taxation: PAYE income tax and National Insurance are deducted at source by the fee payer.
Since the 2017 public sector and 2021 private sector reforms, medium and large end clients determine status, issuing a Status Determination Statement. Many contractors now hold a mix across their recent history — outside IR35 at one client, inside at the next — which is itself a mortgage documentation point this guide addresses.
Outside IR35 applications run on the contract itself. Inside IR35 applications need the gross rate evidenced separately from take-home pay — the packaging difference between gross and net assessment.
The contract, day rate, client and term — plus bank statements showing gross receipts and a work history in the sector. No accounts needed at most lenders.
The contract or agency letter confirming the gross rate, plus payslips, P60s, and the assignment schedule itemising rate and deductions.
The mortgage consequence flows from what arrives in your bank account. Outside IR35, your company receives the gross contract value and the lender can annualise the day rate directly — the cleanest assessment in contractor lending. Inside IR35, your payslip shows income after deductions, and a lender reading only the payslip measures a fraction of your contract value.
The critical distinction is therefore between lenders who assess inside IR35 contractors on the gross contract value — producing a figure close to the outside IR35 equivalent — and those who annualise net take-home. On a £550 day rate, the gap between the two approaches exceeds £200,000 of borrowing capacity. Lender selection is not a refinement for inside IR35 contractors; it is the whole outcome.
Moving between inside and outside IR35 across contracts is now normal, and lenders who understand contracting read the income continuity across the change rather than treating it as disruption. The current contract's status governs the current assessment; the history demonstrates earning consistency. A status change during a mortgage application is more delicate — lenders assess the position at offer, and a material change should be disclosed. We plan application timing around known upcoming changes, because a week's sequencing can preserve an assessment basis worth six figures.
The gross-contract-value lender pool for inside IR35 contractors is established but shorter than contractors assume, spanning several major contractor-friendly names with methodologies that vary in detail — some assess the rate before employer's National Insurance, others after, a difference of around 13.8% in assessable income. Criteria are revised continually, which is why this guide describes the logic rather than reciting a list that would age within months.
Our working knowledge of the live positions — refreshed case by case — is the practical substance of specialist advice. Whatever your status, the principle holds: your IR35 determination is a tax fact, not a borrowing penalty, provided the application lands with a lender whose methodology respects it.
Frequently asked questions