Corporation Tax Late Filing Penalties UK: HMRC Rules

• Filing a CT600 late triggers an automatic £200 fine.
• Fixed fines apply even if your company made a loss or owes zero tax.
• Six-month delays prompt determinations.

Filing an HMRC Corporation Tax return (CT600) late triggers an automatic £200 fixed penalty from day one, rising to £400 after three months, plus 10% tax-geared charges at six and twelve months. These fixed penalties apply even if your private limited company made a loss or owes zero tax.

Many directors confuse the filing date with the payment date. This mistake costs money. Corporation tax is due nine months and one day after your accounting period ends. The CT600 return is due twelve months after your period ends.

Missing that twelve-month mark makes fees jump quickly. After three months, HMRC adds another £200 fine. At six months, officers estimate your bill and add extra percentage fees. Knowing these rules protects your business from harsh penalties.

The statutory penalty timetable for late CT600 returns

Tax inspectors enforce two penalty types: fixed fines and percentage charges. Rates updated in April 2026. Fixed fines land automatically the moment your filing date passes. They do not depend on your tax bill.

A repeat default triggers much harsher terms. If your company files late for three consecutive accounting periods, you count as a repeat offender. In that case, fixed charges jump to £1,000 on day one and £2,000 after three months. If your group runs multiple businesses, see our guide on associated company rules uk corporation tax. It explains how corporate structures divide tax bands.

Fixed fines cannot be avoided by showing zero profits. This surprises many founders. Even dormant firms that received a notice to deliver a return must file on time. Does your company owe money to shareholders? Check our explainer on directors loan account s455 tax to prevent surprise liabilities.

Payment deadlines versus return filing deadlines

One common mistake is assuming tax payment and tax filing share one date. They do not. Under UK tax law, your tax payment deadline arrives three months before your tax return deadline.

For example, if your company year ends on 31 March 2026, your tax payment is due by 1 January 2027. Your CT600 return is not due until 31 March 2027. If you pay late, the revenue authority charges daily interest on the overdue balance. That interest runs separately from filing penalties.

Interest on late tax payments runs from the due date until paid. Pay promptly. Check our guide on trivial benefit rules for directors uk to see which perks stay tax-free.

Worked example: total cost of filing five months late

To see how costs grow, consider an established UK design consultancy. The business owes £15,000 in corporation tax for its year ended 31 March 2026. The director pays the tax on 1 May 2027. That is four months late. Then the director submits the CT600 on 1 September 2027. That filing is five months late.

Because of this, the firm passes the three-month mark but stays under six months. It incurs the day-one £200 fine and the three-month £200 fine. That makes £400 in fixed penalties. No percentage surcharge applies yet because submission arrives before six months. In addition to filing fines, HMRC charges interest on unpaid corporation tax balances. Settle on time. Using our one-hour budget plan helps businesses settle bills on schedule.

Tax determinations issued at six months

When a return remains unfiled six months past its deadline, tax officers step in and take direct enforcement action. The department issues a formal tax determination under Schedule 18 to the Finance Act 1998. Tax officers make this assessment using whatever company data they hold. It serves as an official estimate of your debt.

Inspectors calculate this sum using industry benchmarks or previous trading figures. That official estimate frequently exceeds your actual liability. Officers also add a 10 percent surcharge on the unpaid estimated tax.

You cannot appeal against a tax determination. The only legal remedy is to file your real CT600 return. Once submitted, your actual return replaces the estimate. The surcharge is then recalculated on your true numbers.

Companies House late filing penalties compared

Directors must remember that HMRC filing does not cover Companies House rules. Annual accounts and company tax returns fall under two separate systems. Companies House charges its own civil fines. Missing both means separate penalties from both agencies. Failure to file accounts can also prompt Companies House to strike off your business. Review our guide on statutory sick pay qualifying days for employer rules.

How to appeal an HMRC late filing penalty

You have the right to appeal against a fixed late filing fine if you have a valid excuse. Strict rules apply.

First, file the overdue CT600 return. HMRC requires this step before reviewing any dispute. Second, send your appeal within 30 days of the penalty notice date. Appeal online or write directly to HMRC. A valid excuse must involve an unexpected event beyond your control. Examples include severe illness of the sole director, bereavement, or system failure. General workload pressure or lack of money does not qualify.

Check the HMRC late filing penalties guide and tax penalty appeals rules. Also read the HMRC Corporation Tax penalties manual. Taking early action prevents legal enforcement.

Frequently asked questions