If you are in business then you need to keep your accounting records for 6 years after the end of the business year.
If you are not in business, or are a director of a limited company, then you need to keep records of your personal income for 22 months after the end of the tax year, including details of any claims you make on your Personal Tax Return.
With the recent flooding you may have lost records. If returns have already been prepared, submitted and accepted then this is just unfortunate, and to keep a note or record of what happened to them is a good idea.
However if the records lost are current then you will need to refer to backups and reconstruct as best you can, from bank statements etc. so as to get your returns in on time and with as accurate figures as possible.
This may also be a good time to review your back up procedures and record keeping. HMRC are very happy for you to keep electronic copies. We offer some excellent online accounting systems and our new App has a facility to capture receipts electronically.