When is Corporation Tax due?

For taxable profits up to £1.5 million, 9 months and 1 day after the end of the accounting period.

When is a VAT payment due?

Usually one calendar month and 7 days after the end of the VAT accounting period, which is also the return deadline.

Why put tax dates in a cash forecast?

They are large, known outflows. Leaving them out can hide the week your cash buffer is breached.

Corporation Tax and VAT dates: put them in your 13-week cash forecast

A forecast that shows sales and payroll but leaves out tax dates looks healthier than the business is. Tax payments are the largest known, dated outflows many companies have. They belong in the forecast from week 1.

Corporation Tax

GOV.UK says that with taxable profits of up to £1.5 million you must pay 9 months and 1 day after the end of your accounting period, which is usually your financial year. Above £1.5 million, payment is in instalments, and the rules differ again above £20 million. Check your own band before you place the date.

VAT

If you are VAT registered, you usually send a VAT Return every 3 months, even if you have nothing to pay or reclaim. The deadline for submitting online is usually one calendar month and 7 days after the accounting period ends. This is also the deadline for paying HMRC.

Payment timing

Same or next day: online bank payment, Faster Payments, CHAPS, or debit or corporate credit card.
3 working days: Direct Debit you have used with HMRC before, or Bacs.
5 working days: a new Direct Debit.
Corporation Tax cannot be paid by post.
If a Corporation Tax deadline falls on a weekend or bank holiday, payment should reach HMRC on the last working day before it, unless you pay by Faster Payments. VAT payments must arrive by the deadline even on a weekend or bank holiday.

How it changes the forecast

In the fictional example from our 13-week cash flow guide, opening cash is £35,000 and the base case never falls below £7,800. If you then add a dated VAT payment, the week it clears is the week to check against the buffer. That is the value of dated tax lines: you see when the buffer is tested, not just the total.

Place each tax payment in the week it must clear, not the week you submit.
Show VAT you collect separately from your own revenue, so receipts are not overstated.
Stress customer delay and the tax date together. A late receipt just before a VAT deadline is the pattern that breaks the buffer.
If a payment will not fit, speak to HMRC before the deadline.

General information, not financial, tax or legal advice. The example is fictional. Official guidance checked on 15 October 2026.

A template for this

Practical Finance has built an editable 13-week Excel forecast with a fictional worked example, a blank workbook, a delayed-payment stress test and a cash-buffer dashboard. This article promotes a Practical Finance tool.