What Is IR35 — And Why Does It Still Matter?
IR35 — officially the off-payroll working rules — is HMRC's legislation designed to prevent "disguised employment". In plain terms: if you work like an employee but bill through a limited company, IR35 determines whether you should be taxed like one.
Since the rules were extended to the private sector in April 2021, larger and medium-sized businesses have been responsible for determining a contractor's IR35 status — not the contractor themselves. That hasn't changed in 2026. What has changed is the tax environment around it, and the numbers that make that status determination so financially significant.
Key point: IR35 status directly determines your effective tax rate. At a £500/day rate working 18 days a month, the difference between outside and inside IR35 is typically £8,000–£12,000 in annual take-home pay.
What's Changed for 2026/27?
No sweeping legislative changes hit IR35 in April 2026 — but several tax rate and threshold updates meaningfully affect what contractors actually take home:
Thresholds remain frozen
The personal allowance stays at £12,570 and the higher rate threshold remains at £50,270 — both frozen until April 2028 under current government policy. In practice this is a stealth tax increase: as day rates rise with inflation, more of your income is dragged into the 40% band. A contractor earning £500/day in 2022 and £550/day today pays a higher effective rate even if nothing has changed on paper.
Employer NI increase still in force
The employer National Insurance rate rose to 15% in April 2025, with the threshold dropping to £5,000. Both remain in place for 2026/27. For inside IR35 contractors — where employer NI is deducted from your rate before you see a penny — this is a continuing drag on take-home pay. A contractor billing £500/day inside IR35 effectively loses around £64/day to employer NI alone before income tax is applied.
Corporation Tax unchanged at 19% (small profits)
Outside IR35 contractors using a limited company continue to benefit from the 19% small profits rate on profits up to £50,000. This remains one of the most powerful arguments for maintaining outside IR35 status where the engagement genuinely supports it.
Dividend allowance held at £500
The annual dividend allowance remains at just £500 — down sharply from £2,000 before 2023. Most outside IR35 contractors will pay dividend tax on the vast majority of their dividend income. The basic rate of dividend tax is 8.75%; higher rate is 33.75%.
Outside IR35 vs Inside IR35: The Real Numbers in 2026
Here's what the difference looks like at common day rates, using 18 working days per month (216 days/year) and £3,000 annual expenses for outside IR35:
| Day Rate | Outside IR35 Take-Home | Inside IR35 Take-Home | Difference |
|---|---|---|---|
| £300/day | £43,600 | £36,200 | £7,400 |
| £400/day | £57,100 | £46,900 | £10,200 |
| £500/day | £69,500 | £57,200 | £12,300 |
| £600/day | £81,400 | £66,900 | £14,500 |
| £700/day | £92,900 | £76,100 | £16,800 |
| £800/day | £103,700 | £84,400 | £19,300 |
These are estimates based on 2026/27 tax rates with no student loan, pension, or other deductions. Use our IR35 calculator 2026 to calculate your exact figures.
Reality check: Inside IR35 rates are often negotiated higher to compensate for the tax hit — but rarely enough to fully close the gap. Always model both scenarios before accepting a contract.
How IR35 Status Is Determined
For engagements with medium and large businesses, the end client is responsible for issuing a Status Determination Statement (SDS). This decision should be based on three key employment status tests derived from case law:
- Substitution — Can you send a substitute to do the work? Genuine substitution rights point toward outside IR35.
- Control — Does the client control how, when, and where you work? High levels of control indicate inside IR35.
- Mutuality of Obligation (MOO) — Is the client obliged to offer work and are you obliged to accept it? Ongoing obligation is a hallmark of employment.
Other factors — financial risk, equipment provision, integration into the business — also carry weight. HMRC's CEST (Check Employment Status for Tax) tool remains available, though many contractors and lawyers consider it to favour inside IR35 determinations.
What Contractors Should Do Right Now
The IR35 landscape in 2026 rewards contractors who are proactive rather than reactive. Here's a practical checklist:
- Review your current SDS. If your end client determined you inside IR35, ask for a written explanation. You have the right to challenge the determination via the client's disagreement process.
- Audit your contract and working practices. The contract should reflect reality. If it says you have substitution rights, make sure they genuinely exist.
- Get a professional contract review. Specialist IR35 legal firms (Qdos, Bauer & Cottrell, IR35 Shield) can review your contract and provide an opinion — useful both for peace of mind and as a paper trail.
- Consider IR35 insurance. If you're outside IR35, professional indemnity and IR35 investigation insurance is relatively cheap relative to the potential liability of a HMRC enquiry.
- Model your finances for both outcomes. Use an IR35 calculator to understand what your take-home would be inside vs. outside your current rate — and whether you should negotiate a rate uplift if moved inside.
Small Engagements: The Exemption Worth Knowing
If you work for a small company (meeting at least two of: fewer than 50 employees, turnover under £10.2m, balance sheet under £5.1m), the off-payroll rules do not apply. In this case you remain responsible for your own IR35 assessment, as before April 2021. This exemption still applies in 2026/27 — and it's worth confirming your client's size before assuming medium/large rules govern your engagement.
See exactly what you'd take home
Our free IR35 calculator 2026 covers outside IR35, inside IR35, and self-employed — with a full tax breakdown and monthly/weekly/hourly figures.
Use the IR35 Calculator →Free · No signup · 2026/27 tax rates · Instant results