Self Assessment Software Has an Expiry Date. When Is Yours?

April 2026 came with a quiet deadline that most software vendors never advertised. For the estimated 780,000 sole traders and landlords earning over £50,000 a year, the annual Self Assessment tax return was legally replaced by a new quarterly obligation. The software category millions had relied on for two decades did not disappear from the market. It simply stopped being adequate.

Searching for "self assessment software" in September 2026 is not wrong, exactly. For a significant slice of the self-employed population, it remains the right search. But for hundreds of thousands of others, it is pointing at a product that no longer covers their legal obligation to HMRC. Whether that applies to you depends on one figure: your trading income.

The Product That Stopped Matching the Obligation

Self Assessment software, in its classic form, has a clear purpose: gather your income and expenses for the tax year, calculate your liability, and submit the SA100 return to HMRC by 31 January. For a sole trader earning, say, £38,000 a year from plumbing work, that product still describes exactly what they need. One submission. One deadline. Done.

For that same plumber earning £62,000, the picture changed on 6 April 2026. From that date, HMRC no longer accepts a single annual submission for their business income. The legal requirement is now four quarterly updates, filed digitally through MTD-compatible software, followed by a final declaration confirming the year's figures. Software marketed as "self assessment software" that handles only the January return does not meet that obligation. Filing the old way risks penalties starting at £200 for a single missed quarterly deadline.

HMRC was not discreet about this change. It has been consulting, delaying, and consulting again since 2015. But the gap between policy announcements and market clarity is where most sole traders live, and software vendors have not helped close it.

Three Sole Traders, Three Very Different Situations

The confusion stems partly from the fact that "self assessment software" means genuinely different things depending on your income. There is no single answer. There are three.

Earning over £50,000: You moved to MTD for ITSA on 6 April 2026. Your Self Assessment return for the 2024-25 tax year, filed in January 2025, was your last traditional annual return. From this April, your obligation is quarterly digital updates. Software that handles only the annual SA100 return is now the wrong tool for your situation.

Earning between £30,000 and £50,000: You remain on traditional Self Assessment until 6 April 2027. You have one more annual return to file: the 2025-26 return, due 31 January 2027. After that, you join the quarterly MTD regime. If you are currently shopping for software and expect to stay above £30,000, buying a product that handles only the annual return is a purchase that expires in seven months.

Earning under £30,000: You are on traditional Self Assessment for the foreseeable future. HMRC has not announced a firm date for extending MTD to incomes below £30,000, though the original roadmap included this group. Standard Self Assessment software covers your current obligation.

The practical consequence: if you are in the first group and you search for "self assessment software," many top results show a product that handles one submission per year. You need one that handles five.

Why the Software Market Has Not Caught Up

Software companies have a commercial incentive to describe their products in the terms people already search for. "Self assessment software" is a high-traffic phrase. "MTD for ITSA quarterly submission software" is not. The result is that some products marketed under the self assessment label are fully MTD-capable, and some are not. The label tells you almost nothing useful.

This is not a new observation. As explored in HMRC Compatible Software: What the Label Cannot Tell You, phrases like "HMRC compatible" or "MTD-compatible" carry no standardised meaning in the software market. A product can appear on HMRC's own software list and still fail to cover your specific tax situation. The same ambiguity now applies to "self assessment software" in 2026.

The vendors who benefit most from this confusion are those selling annual-return software at lower price points. They attract customers searching for "self assessment software," onboard them, collect a subscription fee, and rely on the customer not discovering until a penalty arrives that the product does not handle quarterly MTD submissions. It is not fraud. It is marketing that has not updated to reflect the law.

For a sole trader who crossed the £50,000 threshold in April 2026, that discovery often lands in the form of a penalty notice. The software vendor bears no legal liability for the mismatch. The sole trader does.

The Final Declaration Is Not What You Think

Some software vendors market their product as covering "Self Assessment and the MTD final declaration," implying that the final declaration is simply the old annual return under a new name. It is not.

Under MTD for ITSA, the final declaration is a confirmation step that follows four quarterly updates. By the time you reach the final declaration, you have already submitted your income and expenses data to HMRC four times during the year. The final declaration reconciles any adjustments, claims reliefs, and confirms the annual figure. It cannot substitute for the quarterly submissions; it depends on them.

A product that handles only the final declaration, without the quarterly submissions, covers roughly one-fifth of the obligation. Some older Self Assessment tools are being rebranded to mention "final declaration" support without meaningfully changing their quarterly submission capability. Before relying on any software, check what it does between quarterly deadlines: 31 July, 31 October, 31 January, and 30 April.

The Self Employment Accounting Software: The Year-Two Trap covers what happens when sole traders discover this gap after a full cycle of missed quarterly deadlines, rather than at the start of their MTD obligations.

What to Actually Check Before Buying

If you are above the relevant income threshold, your software must do four things.

Quarterly submissions: The software must compile your income and allowable business expenses by quarter and submit them directly to HMRC's MTD API. Software that asks you to export a file and upload it manually does not qualify as MTD-compatible.

Digital record-keeping from source: HMRC requires that business records be kept digitally from the point of transaction. Each invoice and expense must be recorded individually. A spreadsheet of monthly totals does not meet this requirement unless it connects to HMRC-compatible bridging software.

Final declaration: Every product that genuinely supports quarterly MTD submissions also handles the final declaration. This is the less variable feature. The quarterly submission capability is the real test.

Self Assessment for non-trading income: MTD quarterly updates cover self-employment income only. Rental income, dividends, bank interest, and capital gains remain on the annual Self Assessment cycle alongside the MTD regime. Your software either needs to handle both tracks, or you need a clear plan for managing each separately. The annual Self Assessment return does not disappear for most people; it just covers a narrower slice of their total income picture.

The Best Accounting Software for Making Tax Digital: The Exit Test runs through how to test whether your current software meets these requirements before a deadline arrives.

The January 2027 Countdown

If your trading income sits between £30,000 and £50,000, you have a specific window. The 2025-26 Self Assessment return, due 31 January 2027, is your final annual return. From 6 April 2027, you join the quarterly MTD regime.

That gives you roughly seven months to choose software that handles both the January 2027 Self Assessment return and the MTD quarterly submissions starting the following April. Buying a product that handles only the annual return now means a second software decision in spring 2027, with all the data migration and re-setup that implies.

The Free Self Assessment Software: The Migration Problem documents how data migration between tax tools routinely loses historical transaction records, requires manual reconciliation, and creates gaps in digital records that HMRC can query during compliance checks.

If you expect to remain above £30,000 next year, the practical move is to choose software now that covers both the January 2027 Self Assessment return and the MTD quarterly submissions from April 2027. One purchase. Not two.

The Search That Points at the Right Product

The search for "self assessment software" is not broken. It is just unevenly useful depending on where you sit in the income spectrum. Below £30,000, it points at exactly what you need. Above £50,000, it mostly points at products that cover one deadline out of five.

The question to add to any software evaluation is not whether a tool is "MTD-compatible" or "self assessment compatible." Those phrases have become almost meaningless in the current market, as HMRC Compatible Software: What the Label Cannot Tell You sets out at length. The question is simpler: does this product submit quarterly updates to HMRC's MTD API, or does it prepare only an annual return?

If the vendor cannot answer that plainly in their feature list, treat that as an answer.

April 2026 changed what "self assessment software" needs to mean for a large part of the self-employed population. The market's search results have not fully caught up. Your tax obligations already have.