Tax is one of the largest cash outflows a business makes, yet it is often the least well planned. Corporation tax, VAT, PAYE and — for larger companies — quarterly instalment payments each fall due on their own timetable, and a finance team that treats tax as a year-end event rather than a rolling cashflow commitment can find itself scrambling for cash it should have seen coming months earlier. This guide sets out the corporate tax payment calendar and, more importantly, how to turn it into a cashflow forecast a CFO can actually rely on.
📌 The core deadlines at a glance
- Corporation tax (non-large): 9 months and 1 day after the accounting period end
- Corporation tax (large, >£1.5m profits): quarterly instalments in months 7, 10, 13 and 16
- Corporation tax (very large, >£20m): quarterly instalments in months 3, 6, 9 and 12
- CT600 filing: 12 months after the period end (separate from the payment date)
- VAT: normally one month and 7 days after each quarter end
- PAYE/NIC: 22nd of each month (electronic); 19th if paying by post
Corporation tax: the 9-months-and-1-day rule
For most companies, corporation tax is due 9 months and 1 day after the end of the accounting period. A company with a 31 March 2026 year end must pay by 1 January 2027. This is a hard date: interest runs from the day after, with no grace period. Note that the payment deadline comes three months before the CT600 filing deadline (12 months after period end) — so the tax is due before the return that reports it is required. A company that waits until it prepares the return to think about the cash has left it three months too late.
Quarterly instalment payments: the trap for growing companies
The single biggest cashflow shock in corporate tax is the move into quarterly instalment payments (QIPs). Once a company's augmented profits exceed £1.5 million, it stops paying tax nine months after year end and instead pays in four instalments during and shortly after the accounting period itself.
- Large companies (profits £1.5m–£20m): instalments on the 14th of months 7, 10, 13 and 16 from the start of the period
- Very large companies (profits over £20m): instalments in months 3, 6, 9 and 12 — entirely within the accounting period, based on estimated profits
Each instalment is a quarter of the estimated annual liability, so QIPs require the finance team to forecast the full-year tax charge early and revise it each quarter. Get the estimate too low and HMRC charges interest on the underpayment from each instalment date.
⚠️ The associated companies trap
The £1.5m and £20m thresholds are divided by the number of associated companies. A standalone company crosses into QIPs at £1.5m — but a company with three associates crosses at just £375,000 each (£1.5m ÷ 4). Groups routinely underestimate this. If your group is growing or you have added subsidiaries, the QIP trigger point may be far lower than you think.
There is one relief worth knowing: a company entering the large regime for the first time does not have to pay by instalments in that first year unless its profits exceed £10 million. This "year of grace" gives a newly-large company one year's breathing space — but only once, and only below £10m.
Not sure when your tax actually falls due?
We can map your full tax payment calendar to your year end — including whether you are about to cross into quarterly instalments — so cash never surprises you.
VAT, PAYE and the monthly rhythm
Alongside corporation tax sit the regular, high-frequency payments that dominate day-to-day cash:
- VAT is normally due one month and 7 days after each quarter end — so a quarter ending 31 March is payable by 7 May. Businesses on the Annual Accounting Scheme or making payments on account follow different patterns.
- PAYE and NIC are due by the 22nd of each month where paid electronically (the 19th for postal payment). Employers paying under £1,500 a month may qualify to pay quarterly.
- Class 1A NIC on benefits (from the P11D process) is due by 22 July after the tax year.
- PAYE Settlement Agreement (PSA) liabilities are due by 22 October after the tax year.
The annual filing cycle
Beyond payments, the compliance calendar has fixed filing dates that a finance team should hold in a single view:
| Obligation | Deadline |
|---|---|
| CT600 corporation tax return | 12 months after accounting period end |
| Statutory accounts to Companies House (private co.) | 9 months after period end |
| Confirmation statement | Annually, within 14 days of the review date |
| P11D / P11D(b) benefits returns | 6 July after the tax year |
| Employer annual PAYE (final FPS) | On or before the last payday of the tax year |
| VAT returns (standard) | 1 month + 7 days after each quarter |
Turning the calendar into a cashflow forecast
The dates themselves are the easy part. The value a finance leader adds is converting them into a rolling tax cashflow forecast — a single view that answers "how much tax leaves the business, and when, over the next twelve months?" In practice that means:
- Mapping every tax payment to a specific date against the company's own year end, not generic examples
- Estimating the corporation tax charge early — especially if QIPs apply — and revising it quarterly as profits firm up
- Layering the tax calendar onto the wider cashflow forecast, so tax outflows sit alongside payroll, supplier payments and debt service
- Flagging the threshold events — crossing £1.5m profits, adding an associated company, a change of year end — that move the whole timetable
Done well, this is exactly the kind of forward-looking financial control that separates a finance function that reacts from one that plans. It is also where an outsourced tax function earns its place — owning the forecast, watching the thresholds, and making sure a large payment never lands as a surprise. For businesses running a broader finance operation, it sits naturally within a virtual finance office.
✅ Key takeaways — corporate tax cashflow
- Corporation tax is due 9 months and 1 day after period end — three months before the CT600 is filed
- Companies over £1.5m profits pay by quarterly instalments in months 7, 10, 13, 16; over £20m in months 3, 6, 9, 12
- The thresholds are divided by associated companies — groups cross into QIPs far earlier than a standalone company
- A newly-large company gets a one-year grace from instalments, but only below £10m profits
- VAT, PAYE, P11D and PSA each have their own dates — the value is in a single rolling forecast, not a list of deadlines
- Treat tax as an ongoing cash commitment, forecast and revised quarterly, not a year-end event
Frequently asked questions
When is corporation tax due?
For most companies, 9 months and 1 day after the end of the accounting period. A 31 March 2026 year end means payment by 1 January 2027. Interest runs from the day after, with no grace period. The payment deadline is three months before the CT600 filing deadline.
What are quarterly instalment payments (QIPs)?
Companies with augmented profits over £1.5 million must pay corporation tax in four instalments rather than a single payment. Large companies pay on the 14th of months 7, 10, 13 and 16 from the start of the period; very large companies (over £20 million) pay in months 3, 6, 9 and 12.
How do associated companies affect the QIP threshold?
The £1.5 million and £20 million thresholds are divided by the number of associated companies. A company with three associates crosses into QIPs at £375,000 of profit each, not £1.5 million. Groups often underestimate how early this applies.
Is there any relief when a company first becomes large?
Yes. A company entering the large regime for the first time does not have to pay by instalments in that first year unless its profits exceed £10 million. This one-year grace applies only once and only below £10 million.
When are VAT and PAYE due?
VAT is normally due one month and 7 days after each quarter end. PAYE and NIC are due by the 22nd of each month if paid electronically (19th by post). Class 1A NIC on benefits is due by 22 July after the tax year.
Why treat tax as a cashflow forecast rather than a deadline list?
Because tax is one of the largest cash outflows a business makes. Mapping every payment to your own year end, estimating the corporation tax charge early, and revising quarterly turns a set of deadlines into a rolling forecast — so a large payment never lands as a surprise.