What happens if I pay my corporation tax late?

HMRC charges interest on Corporation Tax paid late, calculated daily from the original due date until you pay, and this applies even if you file your return on time. Unlike some other taxes, there isn't usually an automatic fixed penalty just for late payment of Corporation Tax itself, though late filing of the CT600 return does carry its own penalties. If you know you'll struggle to pay, contact HMRC as early as possible, as a Time to Pay arrangement may be available, and your accountant can help you negotiate this.