If you are self-employed on the Isle of Man, four dates shape your entire financial year. Miss one of them and you are either scrambling to catch up or facing a bill you did not see coming. Get them in your diary and everything else becomes manageable.
What are the key dates in the Isle of Man tax year?
6 April: the tax year begins
A new tax year starts. Every pound you earn and every expense you incur from this date forward counts towards the current year. Whether you are a plumber, electrician, hairdresser, or personal trainer, this is your clean slate. Start as you mean to go on.
5 April: the tax year ends
The last day of the tax year. Make sure your income and expenses are recorded against the correct year, particularly for anything near the year end.
How income is recognised at year end depends on the accounting basis you use. Cash accounting and invoice accounting treat it differently. If you are unsure which applies to you, your accountant can confirm.
6 October: filing deadline
Your self-assessment tax return for the previous tax year must be filed with the Assessor of Income Tax by 6 October. For the tax year ending 5 April 2026, for example, your return is due by 6 October 2026.
Missing this deadline results in a £100 penalty, with a further £200 if the return is still outstanding after six months. Having your records in order well before October makes this entirely avoidable.
6 January: Payment on Account
This is the date that catches many sole traders off guard, especially in their first year of self-employment. If you had a tax liability in the previous year, you will likely receive a Payment on Account notice. This is an advance payment towards next year's bill, covering both income tax and National Insurance contributions. The calculations differ between the two. Knowing it is coming in January and setting money aside throughout the year makes it significantly less painful when it arrives.
The key dates every Isle of Man sole trader needs in the diary.
What does this look like in practice?
For most sole traders, the pressure falls in the months between April and October. The return covers the previous tax year, and if records have not been kept throughout the year, this is when the scramble starts.
Six months sounds like plenty of time. It goes quickly when you are running a business.
The sole traders who find October straightforward are the ones who have been recording as they go. Not a Sunday evening reconstruction of six months of receipts, but a few minutes logged after each job, each purchase, each invoice sent.
Tally Up is built for exactly this. As you record income and expenses throughout the year, you get a live running estimate of your income tax liability, National Insurance contributions, and Payment on Account, based on what you have entered so far. Every one of the key dates is displayed right on your dashboard, with a live countdown, so you always know exactly where you stand.
Tally Up displays your key dates and running tax estimate on your dashboard throughout the year.
By the time October comes around, your records are already in order. No scramble. No Sunday evening spreadsheets. Just a review and a submission.