Business tax is mostly a set of fixed dates and a set of kept records. If the difficult part for you is the remembering, the calendar and the filing cabinet, then the useful fix is systems, not effort. This page sets out the dates, what missing one costs at current figures, and the routines that take the dates out of your head.
Nothing here is specialist. It is the ordinary Self Assessment machinery, set out one date at a time.
Three frictions and the system that removes each one
Friction: the deadline lives in your head
Self Assessment has four hard dates. Register by 5 October after the end of your first tax year of trading. Paper returns are due 31 October, online returns and the balancing payment on 31 January, and the second payment on account on 31 July.
Nothing prompts you before these dates except HMRC's own notice, which arrives once and is easy to lose.
The fix: put all four dates in a calendar as recurring annual entries. Give each one a reminder two weeks out and a second three days out.
Then add a fifth entry in early December for "return ready". December is the working deadline; January is the legal one. The point of the gap is that the system fails safely.
Friction: records arrive as loose paper and get lost
Most late returns are late because the records were not ready, not because the date was unknown. Paper receipts have to survive a pocket, a van and a kitchen table to reach the return.
The fix: photograph the receipt where you are standing and let a bookkeeping app store it. HMRC accepts digital copies. Use one business bank account so the statement itself is a near-complete list of what happened. Then a single monthly session, on a fixed day, categorises the month rather than the year.
Friction: the numbers are only ever known in January
If the books are done once a year, you find out what you owe about three weeks before you have to pay it. That is a cash problem as much as a paperwork one.
The fix: reconcile monthly and move a fixed percentage of every payment received into a second account on the day it lands. Standing orders and bank rules can do both without a decision each time. By January the money is already separate and the figure is not a surprise.
What a missed deadline costs
The penalty machinery is Schedule 55 and Schedule 56 of the Finance Act 2009. The figures below were still current when this page was checked in August 2026.
Late filing, in order:
- 1 day late: £100, charged even if you owe no tax
- 3 months late: £10 a day for up to 90 days, a maximum of £900
- 6 months late: £300 or 5% of the tax due, whichever is higher
- 12 months late: £300 or 5% of the tax due again
Late payment is charged separately, and being late on both means both apply. The late-payment penalty is 5% of the unpaid tax at 30 days, again at six months and again at twelve months. Interest runs on top at the Bank of England base rate plus 4 percentage points, which was 8% when this page was checked in August 2026. The calculation below uses that rate; the rate moves with the base rate.
If you cannot pay, a Time to Pay arrangement can be set up online for debts up to £30,000. Filing on time and paying late is cheaper than doing neither, so the return still goes in on the date.
What three months late actually costs
A sole trader running a small joinery business in Chester files and pays on 30 April 2027, three months after the deadline. The 2025/26 return and the balancing payment were due on 31 January 2027. The tax and Class 4 National Insurance due were £4,800.
The charges, using the figures above:
- Late filing: £100. Daily penalties begin the day after the three-month point, so filing on 30 April avoids them by one day.
- Late payment at 30 days: 5% of £4,800 = £240.
- Interest: £4,800 at 8% is £384 a year. The bill is unpaid from 1 February to 30 April, which is 89 days. £384 x 89 / 365 = £93.63.
Total: £100 + £240 + £93.63 = £433.63. Nine days later the daily penalties would have added £90, and they keep running to £900.
The arithmetic points somewhere specific. The fixed £100 is the small part, and the expensive parts are all driven by the tax being unpaid. So the filing and the money are two separate systems, and the money one starts earlier.
What records you actually have to keep
As a sole trader you keep records of your business income, your business expenses, and anything claimed as an allowance. The evidence behind them is invoices, receipts and bank statements. Self-employed records must be kept for at least five years after the 31 January filing deadline for that tax year.
A short list of what makes the year easier:
- One bank account used only for the business
- Receipts photographed at the point of purchase, not collected for later
- A fixed monthly reconciliation slot in the calendar, 30 minutes is usually enough
- Mileage recorded by an app rather than reconstructed at year end
- Invoices raised from software that chases them, so payment does not depend on you noticing
Our page on record keeping for sole traders under Making Tax Digital covers the detail of what a digital record has to contain.
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What Making Tax Digital for Income Tax changes
Making Tax Digital for Income Tax (MTD for Income Tax) replaces the single annual return with digital records, four quarterly updates and a year-end return. It phases in by qualifying income:
- £50,000 and above: from 6 April 2026, tested on 2024/25 income
- £30,000 and above: from 6 April 2027
- £20,000 and above: from 6 April 2028
Qualifying income is gross self-employment and property income added together, before expenses. That is the figure to check, not your profit.
Read plainly, this is more submission dates, not fewer. It is also four smaller events instead of one large one, and software that reads your bank feed prepares most of each update. If January is the month you dread, that shift is usually in your favour. It only works if the software is set up before your start date.
The practical move is to start keeping digital records a year early. That way the first quarterly update is a normal task rather than a new system learned under a deadline. Our Making Tax Digital accountant page sets out what the software has to do.
VAT and the threshold worth automating
You must register for VAT when taxable turnover passes £90,000 in any rolling 12 months. You must also register if you expect to pass it within the next 30 days. Rolling 12 months means any consecutive twelve, not your accounting year.
This is the threshold most often crossed without anyone noticing, because nothing visible happens on the day. Set a running 12-month total in your bookkeeping software with an alert at £75,000. Once registered, VAT returns are quarterly and digital, since MTD for VAT has applied to all VAT-registered businesses since April 2022.
Asking HMRC for adjustments
HMRC runs an extra support service and publishes how to ask for adjustments to how it deals with you. Adjustments can include a different contact method, more time on a call, or information sent in another format. You can ask on a call, in writing, or through your accountant.
The gov.uk page is get help from HMRC if you need extra support. There is also a separate gov.uk page on Access to Work, which is a government scheme covering practical workplace support. Both are linked here as information only. We do not handle applications or claims of any kind, and we are not able to advise on them.
What an accountant actually removes
The value here is not tax cleverness. It is that filing stops depending on your recall, and that someone else is watching the dates and asking for what they need.
Useful questions to ask a firm before you engage it:
- When will you ask me for records, and how far ahead of the deadline?
- How do you send reminders, and can I choose email over phone?
- Will you tell me what I owe well before 31 January, or in January?
- Who do I contact between January and April, when nothing is due?
- What happens if I do not reply to you?
That last one matters most. A firm that has a defined follow-up process is offering a system; a firm that waits for you is offering an invoice. Our Self Assessment accountant page covers what the service normally includes, and the penalties page has the full charge structure and how to appeal.