If you’re a UK contractor working Inside IR35, the received wisdom is: “just use an umbrella, a Limited company is pointless.” That’s almost right, but not quite. This guide walks through when umbrella genuinely wins, when a Ltd company still edges ahead even Inside, and the salary sacrifice trick that can shift the answer by £8,000/year.

Rates used throughout are 2024/25 for rest-of-UK taxpayers.

The short version

  • Inside IR35 + no pension contribution: umbrella and Ltd give nearly identical take-home. Umbrella wins on hassle.
  • Inside IR35 + big pension contribution: umbrella typically wins because employer pension contributions via salary sacrifice fully bypass Employer NI + Apprenticeship Levy.
  • Outside IR35: Ltd wins comfortably. This guide isn’t about that case — see the IR35 calculator for those numbers.
  • The tax rules genuinely are the same for Inside IR35 whether you route via umbrella or Ltd. What differs is the fee structure, admin burden, and how easily you can access salary sacrifice.

Why the tax outcome is (roughly) the same Inside IR35

The IR35 legislation was written to eliminate the tax advantage of using a personal service company. Since April 2021 for medium/large clients, if a role is Inside IR35, the fee-payer must deduct income tax and employee NI as if you were an employee, and the deemed-employer pays Employer NI + Apprenticeship Levy on top.

Whether that fee-payer is an umbrella or your own Ltd, the same deductions must happen:

  1. Assignment rate arrives
  2. Employer NI (13.8% above £9,100) and Apprenticeship Levy (0.5%) come off first — this is a mathematical inevitability, not something the umbrella is “charging extra”
  3. What’s left is your gross salary
  4. Then Income Tax and Employee NI come off that
  5. What’s left lands in your bank

The only structural differences are:

  • Umbrella takes a weekly/monthly margin (£15–£30) for running the payroll
  • Ltd company has accountant fees (~£100–£150/month) and Companies House admin

Everything else — the tax bands, the NI thresholds, the personal allowance taper above £100k — is identical.

Worked example: £500/day, no pension

Let’s take a £500/day contract, working 46 weeks × 5 days = £115,000 assignment rate. Standard tax code, rest-of-UK.

Via umbrella (£25/week margin, 46 weeks worked):

  • Annual assignment rate: £115,000
  • Umbrella margin: £1,150 (25 × 46)
  • Available for salary: £113,850
  • Employer NI (~13.8% above £9,100) + Apprenticeship Levy: ~£13,700
  • Gross salary: ~£100,100
  • Income Tax (bands + taper starts): ~£28,400
  • Employee NI: ~£4,190
  • Take-home: ~£67,500

Via Ltd company (Inside IR35, deemed payment applied by fee-payer):

  • Contract rate: £115,000
  • Accountant: ~£1,500/year (deductible before deemed calc? No — deemed rules use gross fee.)
  • Employer NI + Levy: ~£13,850
  • Deemed salary: ~£101,150
  • Income Tax + Employee NI: ~£32,650
  • Net into personal bank: ~£68,500
  • Minus accountant fees (paid personally or from small residual): ~£1,500
  • Take-home: ~£67,000

Difference: ~£500/year. Effectively a wash. And that’s before the umbrella’s marginal cost is offset by the Ltd’s mandatory paperwork (Confirmation Statement, corporation tax return, personal tax return, VAT if registered).

Run these numbers yourself on the umbrella take-home calculator — the exact answer depends on your student loan status and pension setup, both of which the calculator handles.

Where umbrella pulls ahead: salary sacrifice pensions

This is the underappreciated point that makes umbrella genuinely better for many contractors:

Umbrellas typically offer salary sacrifice pension contributions — where you agree to a lower gross salary and the equivalent amount goes into your pension as an employer contribution. Because it’s an employer contribution, it bypasses:

  • Income Tax
  • Employee NI
  • Employer NI (13.8%)
  • Apprenticeship Levy (0.5%)

That last two matter enormously for contractors. On a £115k assignment, sacrificing £20,000 into pension via a good umbrella saves you:

  • £20,000 × 42% (higher rate + employee NI) = £8,400 of personal tax
  • Plus the Employer NI + Levy that would have applied to the salary equivalent: ~£2,860

Total tax saving: ~£11,260 on a £20k pension contribution — that £20k cost you only ~£8,740 of foregone take-home. Effective cost of 43.7p per £1 in pension.

Even better: for salaries above £100k, sacrificing enough to bring taxable income below £100k restores the personal allowance that would otherwise taper away, giving a marginal effective rate of ~62% on that band. The salary sacrifice calculator shows the exact numbers.

Where Ltd wins Inside IR35: expenses (barely)

Historically the Ltd company advantage Inside IR35 was the ability to claim genuine business expenses (equipment, home office, travel to temporary workplaces) against the small residual. Since 2016 the “temporary workplace” rule was effectively killed for Inside IR35 workers — you generally can’t claim commuting to your engagement.

What’s left:

  • Equipment used for the role (laptop, monitor)
  • Genuinely business-only phone/internet
  • Professional insurance

For most contractors this is £1,500–£3,000/year of expenses that save maybe £600–£1,200 of tax via a Ltd but zero via an umbrella. Not nothing — but usually less than the annual accountant fee.

When umbrella specifically wins

  1. You want to contribute more than £10k/year to pension. The Employer NI savings compound fast.
  2. You want simplicity. No accountant, no Companies House filings, no personal tax return complexity.
  3. You’re mixing Inside and Outside contracts. Running a Ltd only when Outside and umbrella when Inside is a common pattern — but keeping the Ltd open costs ~£1,500/year in accountant fees even when dormant.
  4. You have a Plan 4 student loan. Umbrellas handle student loan deductions cleanly via PAYE. Ltd companies operating Inside IR35 do too, but reconciliation is fiddlier.

When Ltd still wins Inside IR35

  1. You have significant genuine business expenses. Equipment-heavy roles like specialist test kit, imaging, video kit.
  2. You bounce between Inside and Outside frequently. Closing/opening a Ltd is expensive; keeping one alive spreads that cost.
  3. You have a spouse in a lower tax band. Splitting dividends is only possible via Ltd (and only Outside IR35 contracts fully benefit).

Umbrella red flags

Not all umbrellas are equal. Post-2021 the market saw a boom in “tax-efficient” umbrellas offering 85%+ retention — every single one of these is a tax avoidance scheme currently being unwound by HMRC via Loan Charge-style retrospective enforcement. Avoid.

Legitimate umbrellas offering PAYE retention rates:

  • No pension sacrifice: ~55–60% of assignment rate
  • With 20% pension sacrifice: ~70% of gross reaches you + pension combined

Anything higher is a scam. Ask your umbrella:

  • Are you a member of FCSA or Professional Passport?
  • Do you provide a key information document (KID) showing all deductions?
  • Do you use umbrella PAYE, not “elective deduction” or “loan/annuity/fiduciary” arrangements?

The bottom line

For most contractors on Inside IR35 contracts in 2024/25:

  • If you’re not maxing pension — go umbrella. Cheaper, simpler, take-home is within £500/year of Ltd.
  • If you’re maxing pension — definitely go umbrella. Employer NI savings on sacrifice are significant.
  • If you have chunky legitimate business expenses — Ltd still edges it, but the gap is smaller than it was.

Model your specific rate with the umbrella take-home calculator or compare Inside vs Outside directly with the IR35 calculator.

Making the call at renewal? The IR35 Inside vs Outside Decision Kit (£19) puts the 20-question status scorecard, the pension-optimiser for the Ltd path, and the full umbrella waterfall in one Excel workbook — with your assignment rate — so you can share the working with your accountant instead of arguing about it.

Rates and thresholds accurate for UK 2024/25. Not tax advice — consult a qualified accountant before switching structures.