Q: Can someone demand past house pymts over a year later, without sending notice of late pymt EVER?

A: Yes. The statute of limitations for breach of contract is four years. As a condition precedent to collecting attorney fees in a suit for breach of contract, he is required to make a written demand for payment at least thirty days before bringing suit. If you pay the demand within thirty days, he may be precluded from recovering attorney fees.

If it is your position that payment was made, a plea of payment is a special defense that you must plead and prove in accordance with Rule 95 of the Texas Rules of Civil Procedure. A person making a payment would obviously have documentary evidence of the payment having been made (a receipt, a cancelled check, etc.). If you made payments by check, you would be able to tell when you reconciled your bank statement that he had not yet cashed or deposited the check. A reasonable person would take action upon discovering that a payment they made had not yet cleared their bank like contacting the recipient to confirm receipt and to determine if there is an explanation why the payment had not yet cleared. Moreover, the money would still be in your bank account and available to make the payment.

Now, if your written agreement contains a specific provision that requires the Seller to give you notice of non-payment within a specific period of time or payment shall be deemed to have been made (which would be a highly unusual term of such an agreement), you might have an argument that the failure to give notice to you earlier excuses your non-payment.