Inside vs Outside IR35 Explained for 2026/27

What IR35 actually is

IR35, formally called the "intermediaries legislation", was introduced by HMRC in 2000 to address what they call "disguised employment". The idea: contractors who are functionally employees of a single client but operate through a limited company to access tax advantages should be taxed as employees instead.

In practice, IR35 means that for any given contract, you're either:

• Outside IR35: HMRC accepts you're genuinely self-employed for this engagement. You can take your earnings through your Personal Service Company (PSC), paying yourself a small salary plus dividends, and benefit from corporation tax rather than full income tax + NI on the bulk of your earnings.
• Inside IR35: HMRC says this contract is really employment in disguise. Your earnings are taxed as employment income — full PAYE, with employer NI deducted from your contract rate before you see anything.

The financial difference can be £4,000 to £15,000 per year on a typical contract, depending on day rate. At higher rates the gap narrows substantially, which we'll come back to.

The 2021 reform changed who decides

Until April 2021, contractors themselves decided their IR35 status. Predictably, most contractors decided they were outside IR35. HMRC didn't trust this assessment, but enforcement was sporadic.

From April 2021 onwards, for private sector contracts above the small company threshold, the end client decides your IR35 status, not you. They issue a Status Determination Statement (SDS). If they get it wrong and call you outside when you should be inside, the tax liability sits with them — so they err on the side of caution and call most contracts inside IR35.

The practical result: way more contractors are inside IR35 today than were before 2021, regardless of how the work actually looks.

What "Inside IR35" actually costs you

When a contract is inside IR35, the typical setup is umbrella PAYE. Your "contract rate" — the figure on the agency contract — is the amount the agency pays the umbrella. From that, the following deductions happen before you see anything:

1. Umbrella margin: typically £20–£30 per week. Their fee for running payroll.
2. Employer National Insurance: 15% on salary above £5,000 from April 2025. This is deducted from your contract value, not paid extra by anyone.
3. Apprenticeship Levy: 0.5%. Every umbrella over £3m payroll pays it; they deduct from your contract value.

After those, what's left becomes your "deemed taxable salary". Then PAYE income tax (20%/40%/45%) and employee NI (8%/2%) come off. The take-home is what's left.

For a £500/day inside IR35 contract over 220 working days in 2026/27, the net take-home is typically £65,000–£66,000.

What "Outside IR35" actually pays

Outside IR35, you operate through a PSC. The standard tax-efficient setup is:

• Pay yourself a director's salary of £12,570 — the personal allowance — so no income tax on the salary
• Pay employer NI of £1,135.50 on the salary (15% on the bit above £5,000)
• Whatever's left after salary, employer NI, and any allowable expenses is your profit
• Pay corporation tax on the profit: 19% small profits rate, marginal relief £50k–£250k, 25% main rate above £250k
• Take what's left as dividends, paying dividend tax: 10.75% basic, 35.75% higher, 39.35% additional in 2026/27

For a £500/day outside IR35 contract over 220 working days in 2026/27, the net take-home is typically £69,500–£70,500.

The gap narrowed in 2026/27

The Autumn 2025 Budget raised dividend tax by 2 percentage points on basic and higher rate dividends. That only affects outside IR35 contractors, because dividends are how outside IR35 income flows. Inside IR35 contractors pay PAYE, which wasn't changed.

The practical effect: outside IR35 net dropped by about £1,500 per year at £500/day. Inside IR35 net stayed the same. The gap between them narrowed.

At £500/day in 2026/27, the gap is roughly £4,300 per year — outside £69,932 versus inside £65,650 at the same headline rate. To match the outside take-home, an inside contract needs to pay about £545/day. That's a 9% uplift, not the "20–25%" rule of thumb you'll see quoted everywhere else.

Why the uplift required gets smaller at high day rates

Counterintuitively, the higher your day rate, the smaller the uplift you need from inside to outside.

At £1,000/day outside, you only need £1,021/day inside to match — barely 2% more.

Three forces converge above approximately £700/day:

1. Personal allowance fully tapers above £125,140 of total income. Your director's salary becomes fully taxable.
2. Additional rate dividends (39.35%) start to apply to a portion of your dividends.
3. Corporation tax effective rate climbs toward 25% as marginal relief tapers.

The relative advantage of dividend extraction collapses at the very top, so the inside vs outside gap narrows. The widely-quoted "20% uplift" rule of thumb is meaningfully wrong above £700/day.

Who decides your IR35 status now

For private sector contracts above the small company threshold from April 2021 onwards: the end client decides. They issue a Status Determination Statement (SDS).

For public sector contracts: the end client has decided since April 2017.

For small private companies: the rules technically revert to the old system where the contractor decides. In practice this is a narrow case.

If you disagree with the SDS, you can challenge it. HMRC's CEST tool is the official assessment tool, but it's known for being aggressive in calling things inside IR35. A contract review from a specialist is often a stronger basis for challenge than running the same contract through CEST again.

What to do if your contract is inside IR35

• Negotiate harder on rate. Use the actual equivalence number, not rule-of-thumb. Our calculator gives you the specific figure to ask for.
• Get the contract reviewed. A specialist (such as Qdos) can identify whether the "inside" assessment is actually defensible or could be challenged. Most contractors don't bother and accept inside without scrutiny.
• Maximise pension contributions. Inside IR35 through an umbrella, salary sacrifice into pension is highly tax-efficient — it saves both employee NI and employer NI on the contribution amount. Often the single biggest lever available.
• Choose your umbrella carefully. Margins vary £15–£30 per week. That's £400 per year of difference in your pocket for the same service. FCSA-accredited umbrellas are the safest bet.

Conclusion

IR35 isn't going away. The 2021 reform shifted the burden onto end clients, who are predictably cautious. More contracts are inside IR35 than ever.

But the financial gap between inside and outside has narrowed materially in 2026/27. Old rules of thumb are no longer accurate. Run your specific numbers, negotiate based on real figures, and consider whether contract status is challengeable before accepting inside terms.