Practical guide

CT600 filing deadlines

Understand how the standard CT600 filing deadline is set and why it must be tracked separately from the earlier tax payment date.

Why the return deadline still matters after payment

A company can pay Corporation Tax on time and still end up with a late return if the CT600 date is not tracked independently.

The return deadline is therefore its own operational milestone, not just a footnote to the payment date.

Rule summary

Standard CT600 filing timing

In a standard case, the Company Tax Return is due 12 months after the end of the accounting period.

That deadline is later than the ordinary Corporation Tax payment date, so businesses often need both dates visible at the same time.

Worked examples

How the rule behaves in practice

  • Ordinary annual accounting period: A company wants the return deadline for a standard 12-month accounting period. The tool returns the date 12 months after the accounting period end.
  • Keeping payment and filing separate: A business already knows the payment deadline but needs to confirm when the return itself must be filed. The calculator isolates the CT600 date so the return work can be planned properly.

Practical consequences

  • When teams focus only on payment, the return can drift until the company is already exposed to late filing consequences.
  • That risk is avoidable if the filing date is kept visible in the same workflow view as the payment date.

Important limits

  • This tool does not replace detailed professional review where the facts are unusual or contested.
  • If the underlying rule depends on reliefs, appeals, or special handling, the real outcome may differ.

Turn the result into an action plan

  • Use the deadline calculator to anchor the filing date.
  • Move to the late filing penalty tool if the date has already slipped.
  • Keep both tax dates in the same compliance calendar so the work stays sequenced.

Use the tool

CT600 Filing Deadline Calculator

Calculate the standard CT600 filing deadline from the accounting period end using the normal 12-month filing rule.

Related tools

Useful next checks

CT600 Late Filing Penalty Calculator It covers the same compliance topic from the next practical angle. Corporation Tax Payment Deadline Calculator It covers the same compliance topic from the next practical angle. Company Compliance Calendar Generator It extends the workflow into a connected compliance task.

Related guides

Read nearby rule topics

Corporation Tax

Corporation Tax payment deadlines

Understand the standard Corporation Tax payment deadline and why it should be tracked separately from the return-filing date.

Corporation Tax

Corporation Tax late payment penalties

This guide explains why late Corporation Tax payment is not only about the debt itself, but about delay length and repeated default context.