The law does not require a landlord to give you notice of default or amounts in arrears as they occur; a landlord may elect to seek payment of unpaid rent at any time within the statute of limtiations (which means for several years after the nonpayment).If you've paid rent already, you don't have to pay it again. Thus, to the extent you can show payment--have receipts--you will be in a good position. If you can produce receipts to the landlord, he or she should not sue you for any amounts, payment of which you can prove; or if the landlord does attempt to go ahead and sue you, the receipts would provide evidence at trial to show that you do not, in fact, owe those amounts.