The origins of this particular pressure point lie in a structural feature of the British self-assessment regime that many taxpayers discover only when they first encounter a bill large enough to trigger it. For years, HMRC has operated a system of payments on account — a mechanism designed to smooth the collection of income tax from those whose earnings fall outside the automatic reach of PAYE. Rental income, savings interest, private pension receipts, and self-employment profits all fall into this category, and the individuals who receive them have long been required to file self-assessment returns and, where their liability exceeds certain thresholds, to pre-pay estimated tax in two instalments across the calendar year.
The system works as follows. Each payment on account is set at half the previous year’s income tax bill. The first falls due by midnight on 31 January during the tax year itself; the second arrives six months later, on 31 July after the tax year ends. A balancing payment, accounting for any residual liability once actual figures are known, is then due the following 31 January. Taxpayers are exempt from this two-instalment structure only if their last bill came in below £1,000, or if they paid more than 80 per cent of the prior year’s tax at source — through PAYE, for instance. For the remainder, both deadlines carry real force.
That force is now being felt acutely. Saturday, 1 August, marks the point at which HMRC begins applying automatic £100 penalties to those who missed the 31 July payment deadline. The fine is immediate and non-discretionary. Worse, it compounds: a late payment interest rate of 7.75 per cent is applied to all outstanding amounts from the moment they fall overdue, and that interest continues to accrue for as long as the liability remains unsettled. For a taxpayer carrying a meaningful bill into August, the arithmetic deteriorates with each passing week.
Elsa Littlewood, a private client services tax partner at BDO, noted that the timing is particularly unwelcome for many households. Summer, she observed, is already an expensive season — school holidays and childcare costs place additional strain on family budgets at precisely the moment this second instalment falls due. Her advice to those who have already prepared their 2025/26 returns and expect a lower bill than the prior year is to apply to HMRC online to reduce payments on account accordingly, rather than overpaying and waiting for a refund. For those facing genuine difficulty, a Time to Pay arrangement remains available for qualifying debts up to £30,000, accessible via HMRC’s online portal.
Littlewood also flagged a related exposure that some taxpayers may be overlooking entirely. Those who have not yet settled their 31 January 2026 liability — covering the 2024/25 tax year — face a further 5 per cent penalty once that payment reaches six months overdue. Late filing penalties apply separately. The cumulative effect of allowing multiple obligations to drift unpaid can escalate a manageable arrears position into something considerably more serious, and BDO’s counsel is to address outstanding filings and payments as promptly as possible.
Beyond the immediate deadline, a longer-term structural shift is taking shape. HMRC is currently consulting on proposals to move self-assessment tax collection substantially closer to real time, potentially replacing the current annual settlement cycle with monthly or quarterly payment obligations. The stated rationale is to align tax receipts more tightly with the periods in which income is earned. The practical implications, however, are considerably more complex.
BDO has raised a number of substantive concerns about the proposals. The central difficulty is cashflow timing: for the self-employed and for landlords whose tenants pay irregularly or late, a more frequent payment cycle risks demanding tax on income that has not yet been received. There is also the question of transition. During any changeover period, taxpayers could find themselves simultaneously settling obligations under the old annual regime and making payments under the new accelerated one — effectively funding two years of tax within a single calendar year. BDO has indicated it will submit a formal response to the consultation setting out these concerns on behalf of its self-employed and partnership clients.
In the immediate term, a further obligation lands for a substantial cohort of taxpayers within days of the July deadline passing. Some 864,000 sole traders and landlords earning more than £50,000 from self-employment or property are required to submit their first Making Tax Digital for Income Tax quarterly update by 7 August. MTD for Income Tax is now a legal requirement for those within scope, and compliance demands not only that taxpayers are enrolled but that their software is compatible and their summary submission reaches HMRC on time. For those caught by both the payment deadline and the MTD requirement simultaneously, the administrative burden this summer is considerable — and the cost of inattention, measurable.