One of the most confusing parts of Corporation Tax for new business owners is that there is not just one deadline to remember. Your company can have separate deadlines for paying Corporation Tax, submitting its Company Tax Return and filing annual accounts with Companies House. Understanding the difference between these deadlines can help you avoid unnecessary penalties, interest and last-minute problems.

For most companies, Corporation Tax is normally due 9 months and 1 day after the end of the Corporation Tax accounting period. For example, if your accounting period ends on 31 March, the usual Corporation Tax payment deadline would normally fall on 1 January of the following year. Large and very large companies can be subject to different rules and may be required to make Corporation Tax payments by instalments instead.

The deadline for submitting your Company Tax Return is usually 12 months after the end of the accounting period covered by the return. This is later than the usual Corporation Tax payment deadline, which means businesses should not assume they can wait until their tax return filing date before dealing with their Corporation Tax liability. In many cases, the tax will need to be calculated and paid several months before the final filing deadline.

Corporation Tax filings are made to HMRC, while annual company accounts also need to be submitted to Companies House. For an established private limited company, annual accounts are normally due 9 months after the company’s financial year ends, although different deadlines can apply to a company’s first accounts. Keeping your HMRC and Companies House responsibilities clearly separated in your accounting calendar can help prevent important deadlines from being missed.

Missing a Company Tax Return deadline can result in HMRC penalties. For filing dates on or after 1 April 2026, a return that is even one day late can result in a £200 penalty, with another £200 penalty if the return is more than three months late. If the return remains outstanding for six months, HMRC can estimate the Corporation Tax due and apply an additional penalty based on the unpaid tax. Further penalties can apply when the return reaches twelve months late. Repeated late filing can also lead to significantly higher fixed penalties.

Late payment of Corporation Tax is a separate issue from filing the return late. Interest may be charged when Corporation Tax is not paid by the required deadline, so both the payment date and the filing date should be monitored carefully.

Corporation Tax planning should ideally begin well before the end of your company’s accounting period. Keeping your bookkeeping up to date throughout the year allows you to estimate your expected Corporation Tax liability and reserve money for the bill rather than discovering a large amount is due shortly before the payment deadline. Working with an accountant throughout the year can also help identify accounting or tax issues before they become more difficult to resolve.

Good record keeping makes Corporation Tax preparation considerably easier. Your accounting software should be regularly reconciled with your business bank accounts, while invoices, receipts, payroll information, VAT records and significant business purchases should be recorded accurately. Maintaining organised financial records also helps your accountant prepare your annual accounts and Company Tax Return more efficiently.

It can also be helpful to maintain a separate Corporation Tax reserve. Setting aside money for your expected tax liability throughout the year reduces the risk of using funds required for Corporation Tax on everyday business expenses and can make managing your company’s cash flow much easier.

Missing Corporation Tax deadlines can be expensive and stressful. EasyFig can help prepare your company accounts, calculate your Corporation Tax liability and ensure your Company Tax Return is prepared accurately and on time.

Book your free consultation with EasyFig today.