[Your letterhead, if desired; if not, your return address]
[Date of letter-month, day, and year]
[Recipient's first and last names]
[Street or P.O. box address]
[City, State ZIP code]
Dear [recipient's name]:
I was honored to receive the invitation to your company's grand opening festivities taking place on Friday, March 12. I plan to attend, along with one guest, and will be honored to do so.
I look forward to seeing you on the 12th, and congratulations on this significant milestone for your company.
[Sender's first and last names]