ac-co vs untied — which Self Assessment route fits you?
untied is a mobile-first tax app aimed at employed and gig-economy earners, tracking income through the year and filing at the end of it. ac-co is built around a full return with every supplementary page — property, self-employment, capital gains — drafted from your accounts in one pass.
ac-co vs untied, 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 | untiedfrom £64.99/yr |
|---|---|---|
| Price | £29–£65 per return (50% off until 14 January 2027; full price £59–£129) | From £64.99/year (Lite); £129.99/year (Pro) |
| Free to start | Start free, no card — you pay only when you file | 30-day free trial on both plans (not free-until-you-file) |
| Files direct to HMRC | Yes | Yes |
| Who reviews before filing | You review and approve — not an accountant | You — accountant/adviser access is Pro-only and at untied's discretion |
| Supplementary pagesuntied calls out crypto capital gains by name; ac-co supports crypto disposals under SA108 too, just without a dedicated crypto page of its own. | 11 supported — SA102, 103, 104, 105, 106, 108 (shares & crypto), 109 + more | SA102, SA103, SA105, SA108 (names crypto explicitly), SA109 |
| MTD Income Tax quarterly updatesuntied bundles MTD ITSA into its base pricing; ours is still in beta and free to try while signed in. | Beta — quarterly updates drafted from your ledger, on the waitlist | Included in both plans, not a separate add-on |
| 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 — personal tax tracking, not double-entry bookkeeping |
| Mobile app | No — web app only (works fine in a mobile browser) | Yes — iOS and Android |
| Best for | You want a full return — property, self-employment, capital gains — drafted from your accounts in one pass. | You're mainly employed or a gig-economy earner and want an app that tracks everything through the year. |
Competitor details for untied are from untied.io — homepage & pricing (opens in a new tab), checked on 2026-09-10 — check their site for anything that may have changed since. untied is a trademark of its owner; ac-co.ai is not affiliated.
Neither is wrong — it depends what you need.
Pick ac-co if your return spans several income types — self-employment, rental property, dividends, capital gains — and you'd rather it was drafted from your connected accounts in one go than logged through the year in an app.
Pick untied if you're mainly employed or doing gig work, want a phone-first app that nudges you through the tax year, and value MTD Income Tax being included in the base price rather than a beta add-on.
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 untied
ac-co vs untied — why would I move?
I like logging things through the year on my phone.
untied's app is built for exactly that. ac-co is a web app today with no dedicated iOS/Android app — if logging on the go through the year matters most to you, that's a real reason to stay with untied.
untied already includes MTD Income Tax in the price — won't that cost extra with ac-co?
untied bundles MTD ITSA into its base plans. ac-co's MTD Income Tax product is live in beta and free to try while signed in, separate from per-return SA100 pricing — check current terms before you commit either way.
My return is mostly PAYE plus a bit of side income — is ac-co overkill?
untied is built specifically for employed and gig-economy earners, so it may suit a simple profile better. ac-co's strength is a return spanning several income types — self-employment, property, capital gains — drafted together in one pass.
Does ac-co handle crypto the way untied names it?
Yes — ac-co computes capital gains including crypto disposals under SA108, using the same-day/30-day and section 104 pooling rules. untied names crypto explicitly on its site; ac-co doesn't market a dedicated crypto page but covers the same ground.
Do I lose the 30-day free trial untied offers?
ac-co doesn't charge until you file — you can draft your return and see the figure for free rather than trialling for a fixed 30 days.