As well as preparing Statutory Accounts if you are a company, you will also be required to prepare and submit a Corporation tax return (CT600) based on these accounts.
It’s not simply a case of taking the profit figure from the accounts and applying the relevant corporation tax rate (20% in 2016, 19% in 2017). Companies House and HMRC have different rules on how to treat things, so the accounting profit is usually different to the taxable profit.
Your accountant will help you understand these differences, applying all allowances to which you are entitled, to ensure that you are not paying more tax than you necessary and getting the benefits you qualify for.
As with the statutory accounts, the corporation tax amount is due for payment nine months after the period in question. So, if your year end is 31st March 2018, the payment of corporation tax is due by 31st December 2018.