Making Tax Digital for Income Tax Self Assessment (MTD ITSA) went live on 6 April 2026 for sole traders and landlords with qualifying income above £50,000. The single most common plan I hear from owners caught by it is some version of "I'll keep my spreadsheet and use the free software to file." On paper that works. In practice it is the route most likely to earn you penalty points — not because the tools are banned, but because they quietly shift the hardest, most error-prone work onto you, four times a year, forever.
This guide explains exactly where the spreadsheet-and-free-software approach breaks down, and what a setup that actually holds up looks like.
What MTD ITSA actually demands
MTD ITSA is not the old January Self Assessment with a new login. It changes the work itself.
- Digital records, kept throughout the year — not a January reconstruction from a shoebox. Every business transaction must be recorded digitally, in functional compatible software, close to when it happens.
- Four quarterly submissions per income source. One sole trade plus one rental property is eight submissions a year, each due one month and seven days after the quarter end.
- Digital links. Data must flow from your records to HMRC without manual re-keying. Copy-pasting a figure from a spreadsheet into a filing screen breaks the digital link and is not compliant.
- A Final Declaration each January, replacing the old Self Assessment return — where you confirm the figures, make accounting adjustments and add any other income.
- A points-based penalty regime. One point per late quarterly submission; at four points a £200 penalty bites, and every further late submission adds £200.
For the full quarter-by-quarter timetable and the HMRC-compatible software shortlist, see our MTD ITSA quarterly calendar. The point of this article is narrower: why the two cheapest-looking ways of meeting those requirements are the two most likely to fail.
The spreadsheet-and-bridging problem
A spreadsheet alone is not MTD compliant. HMRC is explicit about that. You can keep records in Excel only if you also run HMRC-approved bridging software that reads your spreadsheet and submits to the HMRC API, preserving the digital link.
That is legal. It is also fragile, for reasons that have nothing to do with the bridging tool's quality:
- The digital link is yours to maintain. Bridging software maps specific spreadsheet cells to specific HMRC boxes. Insert a row, rename a tab, or restructure your sheet — something every spreadsheet user does — and the mapping silently breaks. You discover it at submission, against a deadline.
- The spreadsheet itself has no controls. There is no reconciliation, no bank feed, no check that income ties to the bank. A fat-fingered figure or a missed transaction flows straight through to HMRC. The bridging tool submits whatever you give it — including your mistakes.
- It scales badly. One income source is just about manageable. A sole trade plus two rental properties means three sets of records, three mappings, twelve submissions a year. The spreadsheet approach multiplies the manual work by the number of income sources.
- No audit trail. If HMRC queries a figure, "I think I typed it from the bank statement" is not a defence. Proper software keeps the trail; a spreadsheet does not.
Bridging is a compliance bridge, not a bookkeeping system. It will carry you over — and let you fall through the gaps in your own spreadsheet on the way.
Where free software lets you down
The "free" tier looks like the obvious answer. The catch is that free MTD software is built to do one narrow thing — submit — not to keep your books right.
| What free tools typically skimp on | Why it bites you |
|---|---|
| Bank feed quality | Manual entry or weak feeds mean missed and duplicated transactions — overstated or understated income. |
| Multiple income sources | Many free tools handle one sole trade only. A landlord, or a trade plus property, needs separate handling the free tier won't give. |
| Expense categorisation rules | Without rules every transaction is a manual decision — exactly the work that gets skipped and causes errors. |
| Disallowable expense handling | Free tools rarely separate allowable from disallowable spend cleanly, so your quarterly figures are wrong before they're submitted. |
| Support when it breaks | A submission failing 24 hours before deadline with no support line is how penalty points are earned. |
Free software is not a scam — it genuinely submits. But it does the easy part (filing) and leaves you the hard part (keeping the underlying records accurate). MTD penalties are almost never for failing to submit; they are for submitting late because the records were not ready, or submitting wrong figures that unravel at the Final Declaration. Free tools do nothing to protect you from either.
The real cost of the "cheap" route
The spreadsheet-and-free-software plan is chosen to save money. Honestly costed, it usually does not.
- Your time. Reconstructing a quarter's records by hand, four times a year, is realistically 6–15 hours each. Call it 30+ hours a year of your time, at whatever your hour is worth — almost certainly more than £150–£300 of proper software and support.
- Penalty points. Two missed deadlines because the spreadsheet wasn't ready, and you are halfway to a £200 charge, with every subsequent slip adding another £200.
- Wrong tax. Quarterly figures built on uncategorised or duplicated transactions mean an inaccurate tax position all year, and a painful correction at the Final Declaration.
- The January cliff. The whole promise of MTD is no January panic. The cheap route quietly preserves the January panic — you have just added three more mini-panics a year.
"Cheap" that costs you 30 hours and risks £200-a-go penalties is not cheap. It is expensive, paid in a currency the price tag doesn't show.
What a setup that holds up looks like
A setup that survives MTD ITSA quarter after quarter has three parts.
- Proper MTD-compatible software — FreeAgent, Xero, or QuickBooks — with a working bank feed and categorisation rules, so most of each quarter is recorded automatically and accurately as it happens. The cost is real but small, and it removes the manual reconstruction entirely.
- A clean chart of accounts mapped to HMRC's quarterly categories, with allowable and disallowable expenses separated, and each income source kept distinct. Get this right once and every quarterly submission becomes a review, not a rebuild.
- Someone competent owning the rhythm. MTD ITSA is genuinely manageable for a simple single-trade business. It stops being simple the moment you have multiple income streams, mixed-use expenses, or a property portfolio — that is exactly where penalty points are earned. Our MTD for Income Tax service sets up the software, builds the chart-of-accounts mappings, and runs the first quarters with you until the rhythm holds. If you are also a limited company director, your limited company accountant work and your personal MTD ITSA filings need to be coordinated, not run as two disconnected jobs.
If your records are already behind, the first move is a bookkeeping cleanup to get current and reconciled, then the MTD structure on top. And if your current accountant has not even raised MTD ITSA with you, that silence is a warning — our guide on switching your accountant covers moving to someone who is genuinely ready for the regime.
Spreadsheets and free software are not banned. They are simply the tools most likely to let you down — because they hand you the hard, recurring, penalty-bearing work and call it a saving. The honest setup costs a little money and removes the risk. The cheap setup costs your time and keeps the risk.
Get your MTD ITSA setup sense-checked
If you are caught by the £50,000 threshold and your plan is "spreadsheet plus the free tool," let me sanity-check it before the first quarterly deadline rather than after. Fifteen minutes is enough to tell you whether your setup will hold or quietly fail in August.
Send your details and bring the details of your income sources.