Olympic task

My client’s business is arranging hotel bookings in London for German competitors and supporters at the 2012 Olympics.

 He receives a fixed retainer of £2 250 per month for his work from the travel company he is contracted to plus an extra £450 per month advance commission. His final commission from the travel company in 2012 will be based on 4% of the total value of bookings for the travel company.

If this is less than the total of the £450 per month amounts he has received on account he must pay some of this money back.

So if the games are cancelled for example because of a political crisis then he will have to repay the total of the £450s back to the travel company because all the bookings will be void.

For self-assessment purposes is all of the commission taxable in 2012/13 when...