[Your letterhead, if desired; if not, your return address]

[Date of letter-month, day, and year]

[Recipient's first and last names]
[Company name]
[Street or P.O. box address]
[City, State ZIP code]

Dear [recipient's name]:

Well, it's just about that green time of the year-St. Patrick's Day! To wish all of our friends a happy St. Patrick's Day, we are holding a special bash at our house on March 17th at 7 p.m. We will provide drinks, food, and Irish music, and you just have to bring yourself-wearing green, of course! Please RSVP to me by email or phone no later than March 10th.

We hope you'll join us on the 17th. See you then, and Happy St. Patrick's Day!

Sincerely,

[Signature]

[Sender's first and last names]