Many SMEs do their own accounts at year end. If you are one of those folk then you can be reassured that you can continue to use EU adopted IAS (International Accounting Standards) after Brexit. The UK adopted the EU standards some time ago and it is possible that the standards will change at some point in the future but the Government has reassured us that will not happen, if it does happen, until after April 2020.
Further information on Accounting for UK companies post Brexit is available from the Government here