Track company accounts, Corporation Tax payment and CT600 deadlines separately.
The familiar nine-month, nine-month-and-one-day and twelve-month rules describe different obligations and can change for first or unusual periods.
The three common dates
For an established private limited company, annual accounts are commonly due to Companies House nine months after the financial year end. Corporation Tax for profits up to the instalment-payment threshold is usually due nine months and one day after the accounting period. The Company Tax Return is usually due twelve months after the accounting period.
Why the dates can differ
Do not derive every date from one year end without checking.
- The Companies House financial year and HMRC accounting period can differ
- First accounts can cover more than twelve months
- A Corporation Tax return period cannot exceed twelve months
- Large companies can have instalment payment rules
- An approved Companies House extension changes the accounts deadline, not automatically every HMRC date
Set internal control dates
Work back from the statutory dates.
- Bookkeeping close and information request
- Accounts-preparation completion
- Tax-adjustment and computation review
- Director or client approval
- Corporation Tax payment authorisation
- Submission and rejection-resolution buffer
Late filing creates separate consequences
Companies House late-accounts penalties and HMRC Company Tax Return penalties are separate. Missing both deadlines can therefore create more than one penalty stream, while late payment can add interest or other consequences.
Where professional judgement is needed
This guide explains a filing workflow, not the accounting treatment, tax position or legal duties of a particular company. Confirm the applicable accounting framework, reliefs, disclosures and filing obligations against current official guidance and, where needed, a qualified accountant or tax adviser.
FAQ
When are private company accounts usually due?
For an established private company, the usual deadline is nine months after its financial year ends. First accounts can follow a different rule.
When is Corporation Tax usually paid?
For companies within the usual payment regime, the deadline is normally nine months and one day after the accounting period ends.
When is the Company Tax Return due?
It is usually due twelve months after the end of the Corporation Tax accounting period.
Can a first set of accounts require two tax returns?
Yes. A Corporation Tax accounting period cannot exceed twelve months, so a longer first accounts period can require two returns.
Official sources
Checked on 2026-08-11. Official guidance takes priority if rules change.