if you’re self-employed you must keep business records such as your accounts, evidence of tax that’s been paid and other records relating to your income and outgoings. You’ll need these to help you complete your tax return or to answer any questions from HM Revenue & Customs (HMRC) about a return you’ve completed.
As a general rule you should keep your documents for a minimum of 6 years.
If you have to send HMRC a tax return, you should keep all the records and documents you need to enter the correct figures. If HMRC needs to check your return, they may ask to see the records you used to complete it.
If you don’t keep adequate records or if you don’t keep your records for long enough, you may have to pay a penalty.