The whole repayment was due when the home sold in 2011. If they have continued to pay since then, they continued to screw things up. That is why I am suggesting the amended. They could also amend every year subsequent (2012-2017) to get a $500 refund for each of those years and would get it for the open years, but get a "Gee Whiz I am sorry, but your are too late" letter back from IRS.  The good side, you get to charge for all those returns.

I once put a client off until a week after the 3 year statute ran out. It was a several thousand dollar tax credit from some hinky investment scheme. They got a nice "Thank you for filing, but it past the statute date" letter from IRS. The client did not have the money. Everyone in the family had been caught by IRS prior to that and their conscience told them they had to confess. I got paid. They felt better.