Most businesses will need to prepare a set of accounts annually, and these form the basis of your tax return and informs HMRC how much tax is due. Aside from this requirement, a set of accounts can really aid you with the running of your business, as they contain a vast amount of information that can indicate if you need to increase your selling price or reduce your credit terms, for example.
Accounts can be produced as frequently as you need them, monthly, quarterly or annually. So, if you require frequent information about how you business is performing, then monthly management accounts will probably be the best suited to you. If, however, your business is very small, it is likely you have a good idea on how it is generally performing, so you may only then require the annual statutory accounts required for taxation purposes.