You need to keep records if you have to send HMRC tax returns or reports. The type of records you need to keep depend on the returns and reports you need to send to HMRC.
• If you’re self-employed, you must keep records for business income and outgoings. The Self-employed business expenses e-learning explains more https://www.gov.uk/government/news/webinars-emails-and-videos-if-youre-self-employed
• If you’re a director of a limited company, you’ll have company returns and employer returns. There are employer webinars on the records you need to keep for employee returns and expenses and benefits https://www.gov.uk/government/news/webinars-emails-and-videos-on-employing-people
You’ll need your records to fill in your tax returns and reports correctly. If HMRC checks your tax return, they may ask for the documents.
If your business is registered for VAT there are further recording requirements. Find out what you need to do in the ‘VAT – how VAT works’ e-learning https://www.gov.uk/government/news/webinars-emails-and-videos-on-vat