[Your Name, & Address here]
[Recipient Name & address here]
I am in receipt of the invoice [no.] sent by you on [date]. I am writing to inform you that I have already sent you a check [no.] for $[amount] on [date].
In case you don’t receive the check by [date], please inform me on my cell number [no/], and, I will stop payment for this check, and issue a new check to you.
If I don’t get a word from you by this date, I will assume that you have got the check.
Encl: [Enclosures List here]