How can I prove my residence in the UK if I have not kept my documents?
You may still be able to prove your residence through the Settlement Scheme’s automatic check based on your National Insurance Number (NINo). If, however, you were not working, you may be asked for evidence to prove your presence in the UK. The government’s website has a list of documents you can use to prove your residence. https://www.gov.uk/guidance/eu-settlement-scheme-evidence-of-uk-residence
If you do not have any of the documents listed, you may need to apply for pre-settled status with your most recent document and work towards obtaining your previous documents from authorities or wait until you have sufficient evidence to prove a total of 5 years’ residence. If you do not have many documents to show you have been living in the UK then it may be a good idea to talk to one of the Home Office-funded charity / voluntary organisations.
Please remember, you need to make an application to the scheme before 30 June 2021 and prove that you were in the UK before the 31st December 2020 to be granted status under the EU Settlement Scheme.