Your revenue is to show in the month it was earned in and you can explain to your customer that you are unable to change the date for this reason. This does happen from time to time where one does not get an invoice until after the year-end has been closed off. What I do is post the invoice nbr as 12345Mar5/15 and the invoice date as Apr1/15. This helps to explain the expense  was incurred in the previous year but not received until this fiscal year. You could suggest that solution to your customer and that you cannot change your company's books to reflect inaccurate information that you know to not be true.

yes it does make sense, my boss is double checking with the accountants to see what they prefer we do so we are all on the same track.. thanks I will see if your suggestion works.