Dear
Enclosed is our payment in the amount of (amount) which should clear up any balance in our account with you.
We are very sorry that it has taken such a long time to remit our payment to you and we hope that you will understand that we have been experiencing some extremely difficult cash flow problems. We are happy to inform you, however, that we are now on the road to recovery and anticipate a good year.
Thank you for your understanding and the courteousness you have shown our company during this rough period. We are sorry for the inconvenience caused to you and your company.