Self Assessment second payment on account (31 July)

Self-employed individuals and higher-rate taxpayers within Self Assessment make two payments on account each year. The first is due on 31 January, the second on 31 July.

What is this filing?

Payments on account are advance payments toward the following year's tax bill, each equal to half of the prior year's Self Assessment liability (excluding capital gains and student loan repayments). They are reconciled with the actual liability at the next 31 January.

When is it due?

31 July following the tax year for the second payment. The first payment is due 31 January (alongside the SA100 return and the balancing payment for the previous year).

What's the penalty for missing it?

Late payment: 5% surcharge at 30 days late, again at 6 and 12 months. Daily interest at HMRC's published rate accrues from 1 August.

What it actually costs

A 5% surcharge on the unpaid amount applies 30 days after 31 July (i.e. from 30 August). For a client with a £20,000 payment on account outstanding, this is £1,000 immediately. A further 5% applies at six months and again at twelve months. Interest accrues daily from 1 August at HMRC's published rate (currently base rate plus 4%). Unlike the 31 January penalty, there is no flat filing-penalty component — it is purely a payment-on-account surcharge and interest.

Why this catches practices out

• Clients who reduced their payment on account the prior January forget they will owe interest if their actual liability was higher.
• The 31 July deadline is quiet — no one is filing a return — so it is easily missed by both clients and practices not actively monitoring the secondary dates.

How PenaltyProof helps

PenaltyProof's Self Assessment secondary-date monitoring (paid plans) covers 31 July, 5 October registration, and 30 December PAYE-coding deadlines alongside the headline 31 January.

Frequently asked questions

Can a client reduce their payment on account?

Yes. If the client's income is expected to be lower than the prior year, they can apply to reduce payments on account by completing form SA303 online or by post. However, if the actual liability turns out higher than the reduced amount, interest runs on the shortfall from 31 July.

What if the client has paid more than their actual liability?

Overpaid payments on account are repaid after the SA100 or final declaration for the year is submitted. HMRC credits the overpayment at the next January settlement.

Does the 31 July date change for MTD ITSA clients?

No. The 31 July payment-on-account date is unchanged for MTD ITSA clients mandated from April 2026. The same payment schedule applies.

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