It may be a good idea to dust off that old lease and check to see what it says concerning late fees. Late fees are contractually based. If there is no provision in the lease that states a late fee will be charged, then you may not be liable for them. If on the other hand, late fees are provided for in the lease, check to see when the late fees applies. Many leases will not charge a late fee until after the 5th day of the month. If this is the case, check to see when you paid the rent, when the rent was late and how late was the rent, and how much should be charged for the late fees. If you cannot find this information, ask your landlord for the receipts or ledger that he keeps for your rent payments. If your landlord wants to charge you for this money, he/she will have to provide some type of proof.
Notice - This answer was given form informational purposes only and does not create an attorney-client relationship. You should seek the counsel of a local attorney for issues related directly to your claim.