Self Assessment without the January reconstruction
Self Assessment is not hard, it is just done twelve months after the fact. The work in January is usually reconstruction, not filing. Recording as you go turns it into a review.
The dates that matter
For a tax year ending 5 April: register by 5 October if you are newly self-employed, file on paper by 31 October or online by 31 January, and pay any balancing payment by 31 January. Payments on account, if they apply to you, fall on 31 January and 31 July.
Payments on account catch people out
The first January after a good year, you can be asked for the balancing payment for the year just gone plus half of next year's estimated bill, on the same day. That is not an error. It applies where your last bill was above a threshold and most of your tax was not collected at source. Your Self Assessment statement is the authority on whether it applies to you.
What the software does
Taxmo keeps your records digitally, works out the figures, and shows you the return before anything is filed. The figures are traceable back to the entries they came from, which is what you want if HMRC ever asks.
Common questions
Do I need to file a Self Assessment return?
Generally yes if you were self-employed as a sole trader above a small trading level, a partner in a partnership, or had untaxed income HMRC does not already know about. There are other triggers, including high income and certain benefit charges. GOV.UK has a checker that answers this properly for your circumstances.
Can Taxmo submit my Self Assessment to HMRC?
Not yet. It prepares the figures and shows you the return, and direct Self Assessment submission is marked as coming rather than available, so you are not buying on a promise. VAT is already different: Taxmo submits VAT returns to HMRC directly over the Making Tax Digital API today.
What if I cannot pay by 31 January?
Contact HMRC before the deadline about a Time to Pay arrangement. Agreeing one before the due date generally avoids late-payment penalties, though interest still runs. Ignoring it is the expensive option.
Last updated 2026-04-25. Thresholds, rates and allowances are indexed or reset at fiscal events and are deliberately not quoted here; check GOV.UK for current amounts.