Broadly speaking there are always 4 tax years in play. So at the moment we have

2015/16. The tax year just finished. Remember the tax year runs 6th April to following 5th April . This tax year runs 6/4/15 to 5/4/16.

2014/15

2013/14

and

2012/2013.

What can seem like relatively small amounts can add up when taken across four years.