Tenant backdating checks

[Ashley V.]

I have a tenant that has started paying late a couple of times. We usual receive her pmt a day or 2 after the grace period is up. I have noticed that when she drops off checks that she will back date them to the 5th (last day to pay before late fees kick in) even if the check wasn't dropped off until the 6th or 7th. How should I handle this? 

Also she is dropping the checks off to a receptionist and not me directly. Thanks for any input.

[Kim Meredith Hampton]

@Ashley V. can you train the receptionist to look at who has or hasn't paid rent? Our receptionist does not accept checks after the third of the month, and knows that they must have cashiers check or money order.