The Unwanted Lay Bet Calculator is used for cashing out lay bets which have either been placed in error or are no longer required. 

Here is an example of a £5 lay bet at 2.0 which we no longer need. So we put the current back odds into the calculator and it gives us the stake for a back bet to offset the incorrect lay bet:

We can see that our qualifying loss from fixing this incorrect lay would be £0.05. 

You can find a full video tutorial on how to use this calculator here.