Happy Birthday {First Name}!
Everyone here at {Business} is ready to help you celebrate.
So enclosed with this letter, you’ll find a 30% Discount Certificate to be used any time during the month of {Month} at our {Street Address} store on your choice of:
… Or pick something from our latest {Season} collection of {product type} – including the very popular {product}.
But don’t forget - to claim your Birthday Gift, you must use the enclosed certificate before it expires on {date}:
We look forward to celebrating with you!
Sincerely,
{Your Name}
P.S. One more thing: When you bring in this letter you’ll also receive a free "mystery" birthday gift (worth {$$$}) just for coming in, even if you don’t buy anything. So what are you waiting for?