CT600 Filed Late: What HMRC Does and Clearing the Debt
By Oliver Mackman · Reviewed 2026-05-09
You have missed the 12-month filing deadline for the CT600 corporation tax return, or you have filed but cannot pay the corporation tax due 9 months and 1 day after the accounting period end.
What this is
The CT600 is the UK corporation tax return. It must be filed within 12 months of the end of the accounting period. The tax itself is due 9 months and 1 day after period end (so the payment is due before the return). Missing either deadline triggers HMRC late-filing and late-payment regimes that escalate quickly.
What happens if you do nothing
Late filing penalties are fixed and stack: £100 immediately, £100 again at 3 months late, then 10% of unpaid tax at 6 and 12 months. After two consecutive late filings, the £100 fixed penalties rise to £500 each. Late-payment interest runs at 7.75% from 9 January 2026 (base rate plus 4 percentage points). Persistent default can move you onto quarterly instalment payments and trigger a compliance review of older returns. Commercial lenders see late CT600 filings on Companies House (the accounts often track late) and price for it.
Options, in order
- File the CT600 immediately even if you cannot pay. Late filing is a separate offence from late payment and the fixed penalties are escalating.
- Apply for Time to Pay on the corporation tax bill once filed. HMRC accepts most cases under £100k via the online TTP service.
- Use a commercial term loan to clear the bill if the all-in cost is comparable to TTP plus interest. iwoca or Funding Circle quote on soft search.
- For larger bills, asset-backed bridging via Allica or Shawbrook against owned property releases cash without the daily-repayment pressure of an MCA.
- Speak to your accountant before borrowing if multiple corporation tax periods are open or if the underlying P&L has shifted materially.
Which UK lenders engage
- · iwoca for sub-£100k working-capital top-up to clear the bill, same-day decision.
- · Funding Circle for £25k to £500k clean-credit term loans, 1 to 3 day decision.
- · Allica Bank or Shawbrook for asset-backed cases £150k+ against owned property.
- · Just Cashflow for revolving working-capital lines that absorb a one-off corporation tax spike.
- · Specialist HMRC-aware lenders via our broker panel for cases mainstream lenders decline.
HMRC-specific notes
File first, pay second. The two regimes (late filing, late payment) are separate. HMRC almost always grants TTP on a corporation tax bill once the return is filed and the management accounts back the recovery story. Late-payment interest at 7.75% (from 9 January 2026) stacks on the TTP balance, so a commercial term loan at 8% to 12% APR is often a cleaner option once costs are added. The Business Payment Support Service (0300 200 3835) handles HMRC TTP requests for businesses.
Do not do this
- · File a nil CT600 to buy time. That is a separate offence and HMRC may treat the original return as outstanding still.
- · Estimate the corporation tax figure significantly low to reduce the immediate bill. Underdeclaration penalties can reach 100% of the underpaid tax under FA 2007 Schedule 24.
- · Pay corporation tax from a director loan account without ringfencing the accounting; section 455 charges can apply to overdrawn DLAs.
- · Wait for HMRC to chase. The fixed penalty at 6 months (10% of unpaid tax) is the trigger most companies are surprised by; it lands automatically on the system.
When to call an advisor before borrowing
Call your accountant if the CT600 is more than 6 months late, if multiple periods are open, or if the underlying figure is materially uncertain. A licensed insolvency practitioner is the right next step if the bill plus penalties exceeds 25% of annual turnover, or if cash flow does not realistically recover within 12 months.
Related
- · All HMRC pressure scenarios
- · Our post-decline routing (if mainstream lenders have declined)
- · After a decline: alternative lenders
Editorial only. We are not an FCA-authorised adviser or licensed insolvency practitioner. For active enforcement action, contact a licensed insolvency practitioner directly.