Dear

Your letter arrived a few days ago and I must confess
that this obligation completely slipped my mind.
Needless to say, there is no excuse for this and I
extend my sincerest apologies along with the attached
check.

Please accept our warmest regards and sincerest hope
that all is well. We certainly look forward to meeting
you in the near future.

Again, thank you for the hospitality you extended to
us during the vacation period.