ac-co vs GoSimpleTax — which Self Assessment route fits you?
GoSimpleTax is a DIY tax-return product: you fill in guided forms yourself and submit straight to HMRC, on an annual subscription. ac-co drafts the return for you from your connected accounts, and you approve rather than build it box by box.
ac-co vs GoSimpleTax, row by row.
Where we're weaker, we say so. Every ac-co fact comes from our own product pages; every competitor fact comes from their public site, cited below.
| What you get | ac-coSA100 | GoSimpleTaxfrom £69.99/yr |
|---|---|---|
| Price | £29–£65 per return (50% off until 14 January 2027; full price £59–£129) | From £69.99/year (Individual); £96.99/year for Partnership |
| Free to start | Start free, no card — you pay only when you file | Not stated |
| Files direct to HMRC | Yes | Yes |
| Who reviews before filing | You review and approve — not an accountant | You — GoSimpleTax is self-filed, no accountant review offered |
| Supplementary pagesGoSimpleTax also covers SA800 partnership returns (SA801–804), which ac-co does not yet support — an area where it's ahead of us. | 11 supported — SA102, 103, 104, 105, 106, 108 (shares & crypto), 109 + more | SA100–SA109, plus partnership pages SA801–804 |
| MTD Income Tax quarterly updates | Beta — quarterly updates drafted from your ledger, on the waitlist | Separate Making Tax Digital plan, £12.99/month |
| File it from ChatGPT or Claude | Yes — file from ChatGPT, Claude or Codex (MCP) | Not offered |
| Bookkeeping included | Available — ac-co.books (beta), from £9/month | No — integrates with Xero, FreeAgent, FreshBooks and SumUp |
| Mobile appGoSimpleTax's own site doesn't mention a mobile app for the core Self Assessment product (its separate MTD-via-Coconut plan does). | No — web app only (works fine in a mobile browser) | Not stated |
| Best for | You'd rather review a return that's already drafted from your accounts than build one box by box yourself. | You already know your numbers, want to fill the forms in yourself, and prefer one low fixed annual cost. |
Competitor details for GoSimpleTax are from gosimpletax.com/pricing (opens in a new tab), checked on 2026-09-10 — check their site for anything that may have changed since. GoSimpleTax is a trademark of its owner; ac-co.ai is not affiliated.
Neither is wrong — it depends what you need.
Pick ac-co if you'd rather your bank feed, accounts and broker did the box-filling for you — you review a finished draft instead of working through GoSimpleTax's guided forms yourself.
Pick GoSimpleTax if you're confident entering your own figures, want partnership returns (SA800/SA801-804) which we don't cover yet, and prefer one flat annual subscription over a per-return price.
No sign-up — see what you'd owe.
The same income tax engine that drafts your SA100 runs here. Nothing is saved unless you start a return.
An estimate from the figures you enter — not a tax calculation or advice. Your final figure comes from your filed Self Assessment return.
What moves across, and what it costs.
From Other
- ✓Prior-year figures, if you export them
- ✓Your UTR and HMRC login details
Switching from GoSimpleTax
ac-co vs GoSimpleTax — why would I move?
I've already paid for my annual GoSimpleTax licence.
That's a genuine sunk cost — if you're mid-subscription, it may make sense to finish the tax year on GoSimpleTax and move for your next return, where ac-co is priced per return rather than a flat annual fee.
I file a partnership return (SA800) — can ac-co do that?
Not yet. GoSimpleTax explicitly supports SA800 partnership returns with the SA801–804 pages; that's an area where it currently covers more ground than ac-co, and a real reason to stay if that's your situation.
I'm used to filling in the forms myself — won't software drafting it feel like losing control?
You still see and approve every box before it's filed — the difference is ac-co fills them from your connected accounts first, so you're checking a draft rather than building one from scratch.
Is one flat annual fee not simpler than paying per return?
If you file every year regardless of complexity, a flat fee can work out cheaper. ac-co's per-return pricing (from £29) suits filing occasionally or wanting the fee to reflect how complex your actual return is.
What do I lose by moving from a self-filed tool to drafted software?
Nothing about the filing itself — both submit directly to HMRC. What you gain is a draft built from your bank, accounts and HMRC's pre-population instead of typing every box in yourself.