All private limited companies must complete and file an annual company tax return (CT600) to HMRC. When filing your tax return you must work out whether you are liable to pay corporation tax and if so the amount which is owed. You are still required to file a return even if your company made a loss or if you do not have any corporation tax to pay.
Although there is no obligation to use a professional to prepare and file your tax return, many companies do choose to employ the services of an accountant to assist with this process. HMRC can levy financial penalties on any errors which are present on a submitted tax return, therefore, if you have any doubt in your ability to complete this correctly you should enlist an accountant to ensure you are meeting your obligations.