How does everyone handle Social Security payments that were posted prior to learning of the customers death that they aren't entitled to? If we know they are deceased and they come in we return them R15, but what if they posted prior to us learning of the death and we are out of our 2 day return timeframe for R15?

You return them after you find out and wait for the reclamation claim and then give your defense.

How do you return them if R15 can't be used since it's passed the 2 day return timeframe?

You just return it R15. The government isn't going to file a rules violation against you for returning their money.

I meant you return those that are received after you find out that the recipient has died - you are under no obligation to return any other monies unless you get a reclamation claim and there is still money in the account. The government will go after the estate or survivor.

The return limit isn't a government rule, it's a Nacha rule and you do only have the two days to make such a return.

Treasury's reclamation rules protect you from legitimate ignorance of the death, as Randy has said above.