SumTax
UK Self AssessmentBuilt by accountants

Your Self Assessment.
Done in minutes.
Without the accountant’s bill.

Meet SumTax. The AI-powered tax platform built by technology experts and designed and overseen by UK accountants. Calculate, check and submit your return with confidence — from just £79.

Calculate my tax for free See how it works
  • Free to calculate
  • From £79 to submit
  • You approve before filing
Save up to £300UK accountants typically charge £200–£400 to prepare and submit a Self Assessment. SumTax: from £79.
From£79(Free to calculate)
  1. Add your income
  2. We calculate your tax
  3. Accountant-designed checks
  4. Review and confirm
  5. Ready for you to submit to HMRC

Submits direct to HMRC

You approve and submit your own return

Built by tech experts.
Designed and overseen by UK accountants.

Transparent pricing

Free to calculate. Priced by complexity to file.

Free

£0

Your tax calculated, plus instructions to submit on HMRC yourself.

See what's included
  • Simple guided form — no HMRC jargon
  • Instant tax calculation
  • Plain-English explanations
  • Downloadable tax summary
  • Step-by-step instructions to submit on HMRC

You key it into HMRC yourself using our instructions.

Standard

£79

Typically save £170 vs a traditional accountant

Validated and submitted to HMRC by you, in minutes.

See what's included
  • The SumTax Agent: upload documents and chat instead of typing
  • HMRC record sync and discrepancy checks
  • Automated validation against HMRC's rules
  • You submit directly to HMRC from SumTax
  • HMRC submission receipt and reference saved

Premium

£99

Typically save £150+ vs a traditional accountant

Everything in Standard, plus agentic optimisation and planning.

See what's included
  • Everything in Standard
  • Agentic analysis of reliefs and allowances you may be missing
  • Guidance on reliefs such as pensions, Gift Aid and Marriage Allowance
  • Guidance on structuring your affairs for future tax years

You always submit your own return. SumTax is software, not an accountant. Every paid plan includes validation and direct submission to HMRC by you.

Calculate my tax for free

Prices include VAT where applicable. Savings are based on typical UK traditional accountant fees for a similar return and vary by firm. No upsells. Cases outside our supported scope are turned away before payment.

The SumTax Agent · included with paid plans

Throw us everything. The SumTax Agent works it all out.

Get started free
SumTax AgentPaid plans
Here's my P60, and I also rented my flat out from June. Rent was £950 a month.
PDFP60_2025-26.pdf
Got it. Salary £42,180 and £6,020 tax paid from your P60. Rental income of £9,500 for 10 months added. Any letting agent fees or repairs to claim?
Agent took 10%, and I spent £400 on a boiler repair.
Thanks — that's everything. Your estimated bill is ready to view.

Your options

Three ways to do your tax return. Pick the one that suits you.

Do it yourself on HMRC

Free

Best for: Confident filers with simple affairs and time to spare.

  • No cost
  • Full control
  • Tax jargon and long forms
  • Nothing checks your figures
  • Easy to miss reliefs or make mistakes

Traditional accountant

Typically £250–£600+

Best for: Complex affairs: multiple properties, trusts, foreign income.

  • Someone else handles everything
  • Good for complex cases
  • Expensive for most returns
  • Back-and-forth emails
  • Can take weeks

SumTax

Our approach

Free to calculate, submit from £79

Best for: Employees with extra income, freelancers and first-time filers.

  • Free calculation with instructions to file yourself
  • Validated and submitted to HMRC by you, in minutes
  • Premium: agentic analysis of reliefs and future planning
  • You submit your own return — we're software, not an accountant
  • Not for very complex cases yet — we'll tell you upfront
Read the full comparison

Your tax information is important. We treat it that way.

You stay in control

You stay in control

Your data, protected

You approve first

The people behind SumTax

Financial expertise meets intelligent technology.

Meet the team

Questions people ask

Is SumTax secure?

Your documents are stored privately and only you can access them. Connecting HMRC is optional and consent-based — you sign in on HMRC's own website.

Is calculating my tax really free?

Yes. Key your figures into our simple guided form and see your full tax calculation free, with no card needed, plus step-by-step instructions to submit it on HMRC yourself.

What is the SumTax Agent?

The SumTax Agent is our conversational assistant on paid plans. Drop in your P60, payslips, receipts or statements, or just describe your year — it extracts the figures, checks them against your HMRC records and asks only about what is missing.

What's the difference between Standard and Premium?

Standard (£79) validates your return and lets you submit it to HMRC directly. Premium (£99) adds agentic analysis of reliefs and allowances you may be missing, and guidance on structuring your affairs for future tax years.

Does SumTax submit on my behalf?

No. SumTax is software, not an accountancy firm. You review your return, sign the declaration and submit it to HMRC yourself — we make that quick and validated.

Is there an accountant involved?

No. SumTax is a software product. Our tax engine uses published HMRC rules and validates your return before you submit. If your affairs are too complex for software, we tell you upfront.

What if my tax affairs are complicated?

Most situations are supported. A few edge cases, like non-residence, trusts or an open HMRC enquiry, we can't take on yet. We tell you upfront and won't take payment for a case we can't handle.

What if the calculation identifies something uncertain?

We label it clearly as an estimate or open question, and validation won't let you submit until it's resolved.

Tax sorted. Without the usual bill.

Calculate for free. Validate and submit yourself from £79.

Calculate my tax for free