Corporation tax is tax on taxable profit of a limited company. Taxable profit is different from accounting profit. For small companies, corporation tax rate is 20% on taxable profit. Normally, limited company does not have to pay any other taxes than corporation tax.
Small companies have to pay their corporation tax liability by 9 months and 1 day after the year end to H M Revenue and Customs (HMRC). They also have to submit Corporation Tax Return (CT600) by 12 months after the year end. If you do not pay the tax liability in time or submit CT600 in time, there are penalties and interest in addition to corporation tax liability.