At the beginning of January, HMRC estimated that 5.65 million taxpayers had not yet submitted their return. We are now in the final days before the deadline, and any delay can quickly result in automatic penalties, even if no tax is due.
Important: the late filing penalty applies even if your tax liability is zero.
Who needs to file a Self Assessment
You must submit a return for the 2024/25 tax year if you had:
- self-employment income with more than £1,000 in gross turnover
- a share in a partnership
- Capital Gains Tax to pay
- the High Income Child Benefit Charge (if not already dealt with via PAYE)
You may also need to file if you received income not taxed at source, such as:
- rental income
- commissions or tips
- interest, dividends or other investments
- foreign income
The 3 deadlines not to confuse
One of the most common mistakes is confusing filing with payment.
- Online filing deadline
31 January 2026 – 11:59 pm - Tax payment deadline
31 January 2026 – 11:59 pm - PAYE (coding out) option
generally required the return to be submitted by 30 December 2025
Penalties: filing vs payment
HMRC applies penalties separately.
Late filing penalties
- £100 automatic penalty
- after 3 months: £10 per day (up to £900)
- after 6 months: an additional 5% of the tax due or £300
- after 12 months: a further 5% or £300
Late payment penalties
- 5% of unpaid tax at 30 days, 6 months and 12 months
- plus interest
Even if you cannot pay now, submit the return on time.
Why January bills are often higher: Payments on Account
The 31 January payment often includes:
- the balancing payment for 2024/25
- the first payment on account for 2025/26
Payments on account do not apply if:
- your previous year’s tax bill was under £1,000, or
- at least 80% of your tax was already paid at source (e.g. PAYE)
If your income is decreasing, you can apply to reduce payments on account, but underestimating can lead to interest charges.
If HMRC systems are not working
Technical issues may be accepted as a “reasonable excuse”, but only if properly documented.
What to do immediately:
- take screenshots of error messages (ideally showing the time)
- keep a record of dates and access attempts
- retain emails and receipts
- try alternative browsers or devices
Can’t pay? Use Time to Pay
If you’re unable to pay the amount due:
- submit your return first
- then set up a Time to Pay arrangement
For debts up to £30,000, this can often be done online, without calling HMRC.
Refunds: what to realistically expect
Many taxpayers report significant delays in receiving refunds.
Key points to know:
- if you have tax due within 45 days, HMRC may offset the refund instead of paying it
- a “pending” status means the refund is awaiting approval
To follow up correctly:
- check your Self Assessment statement
- verify bank details
- keep a record of communications and evidence
- if delays are excessive, use HMRC’s formal complaints process
Common mistakes (and how to avoid them)
- confusing filing with payment
- accessing your account only at the last minute
- overlooking payments on account
- ignoring Time to Pay
- relying on a refund without checking for offsets
- failing to keep evidence of technical issues
Mini action plan (30–45 minutes)
- check whether you need to file a Self Assessment
- confirm access to Government Gateway and 2FA
- gather key information (income, interest, rental income, pensions)
- check whether payments on account apply
- decide: full payment or Time to Pay (after filing)
Author: Angelo Chirulli, Tax Advisor, Diacron London