How I write a letter of apology?

Question

I was invited to participate in a competition . I am not able to do so for my personals reason which I can not explain in the letter. Pleas help me to write a nice letter. it is such a bad situation for me.

Answer 1

Keep it simple.... Here:

"I am so sorry, but I am unable to attend the competition due to a prior engagement.  Please accept my sincere apologies."

There is never a NEED to "explain" why or what the prior engagement is.  They don't need to know.  Even if you have no prior engagement, they don't need to know that either.

Have a polite day.

Answer 2

Thank the person for the invitation, and state you have a previous engagement already planned.