by Catherine Scott on Wed Feb 23, 2011 7:33 am
A good starting point would be to look at
http://www.hmrc.gov.uk/undeclaredincome/gettingstarted/tax-affairs.htm#6
HMRC will take a view on penalties, but these will always be lower if you go to them, rather than them finding you - As long as you you tell them everything when you do.
Is the £700 the money your b/f has received, or the profit he has made (ie after costs ?) It could be that there is very little tax due.
That said, just because your b/f has made some money does not neccessarily mean he has been carrying on a business that HMRC needs to be told about - could you give us some more information (ie what your bf does, how many sales he has made, how he charges people etc) ?