Contractor tax in one paragraph: if your engagement is outside IR35, a Personal Service Company (Ltd) is usually the most tax-efficient route — director's salary + dividends + employer pension. If inside IR35, the public-sector or large-private-sector engager is responsible for assessing and the contractor is paid as a deemed employee — usually via umbrella. Most contractors in 2026/27 are inside-IR35 by default since the 2021 off-payroll reforms moved status determination to the engager. Negotiating outside-IR35 status remains possible but requires specific working practices.
The three tax regimes
| Route | Who decides status | How paid | Tax efficiency |
|---|---|---|---|
| Outside IR35 + Ltd Co | You (sole director) | Salary + dividends + pension | Highest (typically 80-85% net of gross) |
| Inside IR35 + umbrella PAYE | Engager | PAYE through umbrella | Lowest (typically 60-65% net of gross) |
| Inside IR35 + Ltd Co (deemed employment) | Engager | Engager deducts as if employed; you receive in Ltd as employment income | Slightly better than umbrella due to potential expense claims |
| Sole trader / direct engagement | You | Self-employment, Self Assessment | Rare for IT contracting — most clients prefer corporate engagement |
Inside vs Outside IR35 — the actual test
IR35 distinguishes "disguised employment" (inside) from genuine business engagement (outside). The four main tests, from HMRC's CEST tool and case law:
- Personal service: can you send a substitute? Inside-IR35 if the contract requires you personally.
- Control: does the client direct how, when, and where you work? Inside if yes.
- Mutuality of obligation: is the client obliged to offer further work and you to accept it? Inside if there's an implicit ongoing relationship.
- Part and parcel of the organisation: are you essentially an integrated team member?
Other factors: financial risk (you bear it?), provision of equipment, intent of both parties, exclusivity, payment structure.
The CEST tool: gov.uk/CEST. HMRC says it gives the right answer in 85% of cases. Independent reviews suggest 70-75%.
Outside-IR35 Ltd Co — the optimal extraction
If you can engage outside IR35, a single-director Ltd company allows:
- Director's salary £12,570/year: uses full Personal Allowance, builds State Pension NI credits
- Dividends up to basic-rate band: 8.75% above £500 dividend allowance, on profits after CT (19-25%)
- Employer pension contributions: deductible against CT, no personal tax or NI. Most efficient extraction at higher day-rates
- Retained reserves: for closure-time ifet extraction (14% rate rising to 18% from April 2026) up to £1m lifetime
Worked example: £700/day contractor, ~220 working days/year = £154,000 gross. Outside-IR35:
- Salary £12,570, employer NI cost £1,136
- CT on remaining ~£140k profit: ~£35,000 at es up most of
- Dividend take-home approximately £75,000 (basic rate + part higher rate)
- Pension contribution £40,000 (uses up most of AA)
- Total personal take + pension contribution: ~£128,000 (83% of gross)
Same engagement inside-IR35 via umbrella:
- Umbrella deducts: PAYE income tax + employee NI + employer NI + Apprenticeship Levy + umbrella fee
- Net take-home: roughly £92,000 (60% of gross)
The difference: £36,000/year. Over a 5-year contract, £180,000 of extra after-tax value from outside-IR35 status — if it can be defended.
The 2021 off-payroll reform — what changed
From April 2021 (large + medium private sector) and earlier for public sector:
- The end client (not the contractor) determines IR35 status
- If determined inside-IR35, the fee-payer (agency or client) must deduct income tax and NI before paying the PSC
- The contractor receives net-of-tax payments into their Ltd
- "Status Determination Statement" (SDS) must be issued to the contractor
- Contractors can dispute via client-led appeal process
The reform pushed many engagers to blanket-determine all contractors inside-IR35 to avoid HMRC enforcement risk. Genuinely-outside contractors have had to argue their case more actively, sometimes negotiating specific contract wording or moving to consulting-firm-of-record arrangements.
Umbrella company mechanics
If working via umbrella (inside-IR35 or by client preference), expect:
- Gross rate from agency to umbrella (e.g., £700/day)
- Employer NI deducted at 15% = ~£105 (the umbrella deducts this from your gross because they're "your employer")
- Apprenticeship Levy deducted at 0.5%
- Umbrella margin/fee typically £15-£30/week
- Holiday pay element — either rolled-up or accrued
- Net pay processed through PAYE: PA + income tax + employee NI
Some umbrellas operate "salary sacrifice into pension" which can recover some efficiency for higher earners. Others operate "expenses" claims that HMRC has largely shut down post-2016.
Avoid: any umbrella promising you "85% take-home" — these are usually loan schemes or non-compliant structures that have led to massive HMRC settlements for users.
Allowable contractor expenses
Outside-IR35 (in your Ltd):
- Travel to a "temporary workplace": deductible against company income. Definition: client site where work is expected to last under 24 months. Once 24 months at the same site, it becomes a "permanent workplace" and travel costs become BIK
- Subsistence on overnight stays: reasonable hotel + meal costs
- Home office: simplified £6/week or actual proportion of household costs
- Equipment: laptop, monitor, phone — capital allowances or AIA if substantial
- Training: deductible if maintaining skills, not extending into new fields
- Professional subscriptions: BCS, IET, etc. if on HMRC List 3
- Accountancy fees: fully deductible
Inside-IR35: very few expenses are claimable from the deemed employment income. The 2016 "T&S" (travel and subsistence) restriction effectively ended most expense claims for contractors inside SDC (supervision, direction or control) of an end client.
Common contractor tax mistakes
- Assuming you're "outside" because the contract says so. Working practices matter more than contract terms. HMRC investigations look at how you actually work, not what the contract claims.
- Joining a "high take-home" umbrella scheme. If it promises >75% net of gross, it's almost certainly non-compliant. The Loan Charge will catch you.
- Not separating personal and company expenses. i>Forgetting th chaos plus S455 risks.
- Drawing dividends without distributable reserves. Illegal under Companies Act, reclassified by HMRC as DLA — triggering tax.
- Forgetting the 24-month rule on workplace travel. If you've been at the same client site for 23 months, plan a meaningful change to reset the clock — or accept that future travel becomes taxable.
- Closing a company at the wrong time relative to BADR rate changes. The 10% → 14% → 18% trajectory of BADR makes timing critical for accumulated reserves.
Sources
Related profession-specific guides
How UK Tax Drag holds itself to account
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