Self Assessment and Making Tax Digital
The tax year runs to 5 April. What follows is a sequence of dates that is entirely predictable, which is exactly why running out of money to pay is avoidable.
On This Page
- The Calendar
- Why the Second Year Hurts
- What Making Tax Digital Changed
- How Much to Set Aside
The Calendar
- 5 October
- Deadline to register for Self Assessment if you started self-employment in the tax year that ended the previous April.
- 31 January
- Deadline to file the online return for the tax year ending the previous 5 April, and to pay the balance owing plus the first payment on account for the current year.
- 31 July
- Second payment on account for the current tax year.
- Quarterly under Making Tax Digital
- Where MTD for Income Tax applies to you, quarterly updates are submitted through compatible software during the year, followed by a final declaration after the year end.
Why the Second Year Hurts
In your first year you pay the tax on that year. In your second, you pay the balance for year one plus a payment on account for year two, which is set at half of your year one liability. The January bill can therefore be around one and a half times what you were expecting.
Nothing has gone wrong when this happens. It is simply the system catching up, and it is the single most common cause of a locum discovering they have not put enough aside.
What Making Tax Digital Changed
Making Tax Digital for Income Tax started in April 2026 for sole traders and landlords with qualifying income above £50,000. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028.
If you are in scope, you keep digital records in compatible software and submit quarterly updates, then a final declaration. Qualifying income is measured on gross income before expenses, which means a locum with a turnover above the threshold is in scope even if profit after costs is below it. That surprises people.
How Much to Set Aside
A rough working figure for many locums is somewhere around a third of profit, held in a separate account, adjusted once you know your actual rate and once payments on account begin. We give clients a specific figure based on their own numbers rather than a rule, because student loan repayments, other income and pension contributions all move it.
Last reviewed 3 August 2026. [REVIEWER DETAILS REQUIRED BEFORE PUBLICATION]
Frequently Asked Questions
Can I reduce my payments on account?
Does Making Tax Digital apply to me?
What if I file late?
Get a Tax Figure You Can Plan Around
We give locum clients their tax number well ahead of the deadline, including payments on account, so January is arithmetic rather than a shock.