Ask most owner-directors when their return is due and they will tell you without pausing. Ask what they owe and the answer is usually a guess, a shrug, or a figure from last year that they hope still holds. The date is public information. The number is personal, and it is the only part that affects your bank balance. The gap between the two is where the damage happens, because a date you can diarise and a figure you have to fund are different kinds of problem. One needs a calendar entry. The other needs several months of notice.

By the time a January figure lands, the tax year it relates to closed on 5 April 2026. Every decision that could have changed the number, how much came out as dividends, when it came out, whether a pension contribution made sense, was taken and settled long ago. What is left is arithmetic.

You then pay from whatever cash happens to be in the account in late January, which is often the thinnest point of the year for a consultancy or a trades business with Christmas behind it. The bill is no larger because you found out late. It simply arrives with none of your options attached to it.

For the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026, GOV.UK’s deadlines guidance sets 11:59pm on 31 January 2027 for both the online return and the payment. Paper returns had to be in by 31 October 2026. If you wanted the bill collected through your tax code, that had to be submitted by 30 December 2026, and anyone filing for the first time needed to notify HMRC by 5 October 2026.

One further change is worth noting. Sole traders and landlords with qualifying income over £50,000 come into Making Tax Digital for Income Tax from 6 April 2026, so the reporting rhythm shifts for them.

HMRC reported more than 11.48 million returns filed by 31 January for the 2024/25 tax year, with 97.25% of them submitted online, and estimated that around a million people missed the date altogether. The volume tells you something about how much of the profession works. For a lot of firms, self assessment is a January production line: records requested in December, return prepared in January, figure emailed out, payment due within weeks.

Nothing in that process is wrong and the return is usually correct. It is simply late as a piece of information. You receive a number and about three weeks to find it, which is a cash flow event dressed up as an administrative one.

The distinction matters more than it sounds. Filing is a reporting obligation with a fixed date attached. Planning is a set of decisions that only exist while the tax year is still open. Once 5 April has passed, the dividend you took in February is a fact, the salary level is a fact, and the pension contribution you did not make stays unmade.

An accountant working to the filing date is doing accurate work on a year that has already closed. The information is true and it cannot change anything. The only variable left at that stage is how calmly you can fund the result.

Take a familiar set-up. The director of an established limited company draws a modest salary through payroll and takes the rest of their income as dividends. The company is profitable, the work is steady, and money comes out when it is needed: a quarterly transfer, a larger one when a big invoice clears, something extra in December.

Each movement is reasonable on its own and perfectly legitimate. Nobody is being careless. This is how most of the consultants, contractors and trades businesses we work with pay themselves, and it works well right up to the point where nobody adds the year up.

The dividends crossed into the higher rate band during the year and nothing in the process flagged it. Each payment looked small in isolation. Some were recorded as directors’ loan movements to be tidied up later. There was no running total anywhere, because the company’s books were being brought up to date in batches and the personal position was treated as a separate job for January.

A dividend taken in February at the higher rate costs the same as one taken in July. The difference is that in July there is still a choice about whether to take it, defer it, or structure the pay differently for the rest of the year.

None of this surfaces while the file sits unopened. The return was started in the second week of January, which left a fortnight for questions about bank entries from the previous spring, a missing dividend voucher and a pension statement nobody could locate. Queries sat in an inbox for days while the clock kept running.

HMRC’s figures for the 2024/25 season show 475,722 people filing on the final day itself, and 27,456 in the last hour before midnight, so this behaviour is widespread rather than unusual. Pressure at that stage produces a filed return. It does not produce better decisions.

HMRC’s penalty guidance is straightforward. A return filed late attracts an initial £100 penalty, which applies even where there is no tax to pay. After three months, daily penalties of £10 run up to a maximum of £900. At six months there is a further charge of 5% of the tax due or £300, whichever is greater, and the same again at twelve months.

Late payment is charged separately: 5% of the unpaid tax at 30 days, six months and twelve months, with interest on the amount owed on top. For a director already short of cash in January, that is the worst possible compounding.

Our approach is to treat the director’s self assessment as part of the company routine rather than a January exercise. The bookkeeping is kept current, so the salary and dividend position is visible during the year, and we pull the personal figures in the autumn.

That produces a number with months left before 31 January 2027, which is enough time to set cash aside deliberately, time a dividend sensibly, or decide that something in the pay structure should change for the year ahead. It is the same principle behind forecasting corporation tax a month before the bill lands. The work is not harder. It is earlier.

Knowing the number in the autumn does more than remove the scramble. It changes what comes out of the company between then and the following April, because you can see where the dividends already sit before you take the next one.

It also makes payments on account predictable. Where you make them, the second instalment falls due on 31 July, and that is the one that catches directors out, arriving six months after the first when the cash has been allocated to something else. Seen in advance, it is a line in a plan. Seen in July with no warning, it is a problem.

31 January 2027 is not moving, and a version of it will keep arriving once a year for as long as you are a director. What is negotiable is whether you meet it holding a figure you have known about since the autumn, or one you learned about a fortnight earlier.

If you do not know your number yet, that is a fair question to put to whoever prepares your return, and a fair thing to expect an answer to before December. The right answer is a figure with the working behind it, rather than a promise to look at it closer to the time.