Both apps are mobile-first and affordable, but only one was built specifically around MTD for Income Tax from the ground up. Here is the honest difference.
When two apps sit at roughly the same price point and both claim to be the simple, mobile-first choice for UK sole traders, the decision stops being about cost and starts being about conviction. Untied has been quietly serving self-employed people for years; TapTax was designed from scratch with MTD for Income Tax as the spine of the whole product, not a feature bolted on later.
The single biggest deciding factor in this matchup is not price, it is trajectory and depth. Both apps are affordable and both will get you through a Self Assessment return. Where they diverge is in how much they help you during the year, not just at filing time, and how confidently they are built around the new quarterly-update world that is now mandatory for sole traders earning over £50,000 from April 2026.
Untied began life as a personal tax app, a smarter way to file your Self Assessment return from your phone. It later added MTD for Income Tax support as the regulation moved from proposal to reality. That history shows in the product: the Self Assessment journey is polished, the interface is clean, and it does a respectable job of handling quarterly updates.
TapTax was designed the other way around. The quarterly filing workflow, the bank connection, the AI categorisation of every expense, the receipt scanner that captures a photo and logs the transaction without you typing a single field: all of that was in the brief from day one. The Self Assessment return is not the product; the year-round MTD compliance cycle is. That is a meaningful structural difference when you are a sole trader who now has four quarterly deadlines every year on top of the annual one. You can check every one of those MTD deadlines for 2026, 2027 and 2028 in one place if you want to map out the calendar now.
| Feature | TapTax Free | TapTax Starter | TapTax Pro | Untied |
|---|---|---|---|---|
| Monthly cost | £0 | £4.99 | £9.99 | ~£5-£10 |
| Annual cost | £0 | £59.88 | £119.88 | ~£60-£120 |
| Built for | UK sole traders and MTD | UK sole traders and MTD | UK sole traders and MTD | Self-employed and individuals |
| MTD ITSA quarterly filing | Yes | Yes | Yes | Yes |
| Bank feed connection | Limited | Yes | Yes | Varies by tier |
| AI expense categorisation | No | Yes | Yes | No |
| Receipt scanning | No | Yes | Yes | Limited |
| Mobile-first design | Yes | Yes | Yes | Yes |
| Invoicing | No | No | No | No |
| Self Assessment return | Yes | Yes | Yes | Yes |
| UK-headquartered, sole trader focus | Yes | Yes | Yes | Yes |
At the paid tier, these two apps cost roughly the same. The difference is what that money buys you day to day. TapTax Starter at £4.99 per month includes bank feeds and AI categorisation, which means your income and expenses are being sorted automatically throughout the year, not manually keyed in the week before a quarterly deadline. Untied's comparable tier is a cleaner, more manual experience.
For a sole trader turning over £60,000 and facing four quarterly submissions a year, the administrative saving from automatic categorisation is real and recurring. It is not about the £5 difference in monthly fees; it is about the hour or two per quarter you get back.
Both apps will satisfy HMRC's requirements. Both can submit the quarterly updates and the end-of-period statement that replace the old single Self Assessment return. The question is how much friction sits between you and that submission.
TapTax is built so that the quarterly filing is a one-tap action once your transactions are categorised, and because the AI has been working through the year, most of them already are. The sole trader tax calculator on the TapTax site also lets you sense-check your position at any point in the year, which is useful when you are trying to decide whether to buy equipment before the quarter closes.
Untied handles the compliance mechanics competently, but the workflow is more sequential: you enter or review data, then file. If you prefer to have full manual visibility at every step, that is actually a feature. If you want the categorisation done in the background so you can concentrate on your work, untied asks more of you.
Untied has been in the market longer, which means a more established user base, more community knowledge and a track record of surviving multiple HMRC API changes without disappearing. For a sole trader who is risk-averse about fintech longevity, that history is not nothing.
Untied also has a clean, simple interface that some users will prefer precisely because it does not try to automate everything. If you are a self-employed person with straightforward income, very few expenses, and a preference for reviewing every line before it goes to HMRC, untied's more deliberate workflow suits that temperament.
And for anyone sitting below the £50,000 MTD threshold who is still voluntarily going digital, untied's Self Assessment roots make it a solid, uncomplicated option.
Both apps are genuinely mobile-first, not desktop tools with a mobile version grafted on. You can complete the entire compliance cycle on your phone with either product. The distinction is in the day-to-day texture. TapTax uses your bank connection to pull in transactions automatically, so the app is doing background work even on weeks when you do not open it. Untied is more of a dedicated-session tool: you go in, you work, you file.
The quarterly planner tool on TapTax's site complements the app nicely if you want to map out your income and expenses across the four quarters and see where you stand before you commit to a submission.
You have dozens of supplier transactions a month, mixed personal and business card spending, and approximately zero interest in categorising receipts on a Sunday evening. TapTax's AI categorisation and bank feed will do most of that work for you. The quarterly filing becomes a review-and-tap action rather than a data-entry project. TapTax Starter at £4.99 per month is the call here.
You earn from a handful of clients, your expenses are modest and predictable, and you like to stay hands-on with your numbers. Untied's clean, manual-friendly interface is a reasonable fit. You do not necessarily need AI to categorise three regular expenses, and you may prefer the transparency of entering everything yourself.
You need to be MTD-ready before April 2026, and you need confidence that the app you choose was built for that world, not adapted to it. TapTax's MTD-first architecture gives it the edge here. The transition to quarterly reporting is less jarring when the app has been designed around that rhythm from the start.
Untied is a legitimate, affordable option and it deserves credit for sticking around in a market that has seen better-funded rivals come and go. But TapTax was built to solve the specific problem of making MTD for Income Tax manageable for a sole trader who would rather be doing their actual job. The bank feeds, the AI, the receipt scanner and the one-tap quarterly filing are not extras; they are the whole point.
If you are above the MTD threshold, or heading there, and you want software that treats quarterly compliance as a year-round process rather than a deadline scramble, TapTax is the more purposeful choice at roughly the same price.
Same price bracket, different philosophy: untied asks you to manage your tax; TapTax manages it around you.
TapTax connects to your bank, categorises expenses automatically, and submits quarterly updates to HMRC. Free plan, no card required.
