here is what I 'remember', (no doubt I've forgotten a few), 'refunds' I was owed, still owed, and will never collect.
1983 - $1,400 for payroll taxes
1990 (or thereabouts) $2,000 overpayment never refunded.
2005 - $500 overpayment, never refunded.
Now I hope you aren't about to ask, "Didn't you contact them, complain, demand the refund".... because the answer to that, obviously, is YES... many, many, many times.
In the case of the 1983 payroll mistake here's how that went.... they said I owed $1,400... I went into the IRS and proved I didn't, had all my records. They agreed. Got another bill for it about 6 months later. Went in again, they agreed again. Next year another bill, this time with penalties added... went in again, proved it again.
The following year, another bill. Went in again... they told me to only way to clear it was to pay it and then they'd refund me. I told them to go to hell. Next year... another bill, more penalties. My Dad convinced to pay it... so I paid the $1,400 I did not owe... next year... another bill for $1,400 saying they hadn't received the money.... showed them the cancelled check, they agreed they had received it and I would be refunded. I wasn't... Next year.. another bill, same amount, year after that another bill, same amount. This went on....
For nearly a decade... I think it was 8 years. I just started ignoring it... my attitude was come and get me if you can. After 8 years I stopped receiving the bill... I was never refunded the $1,400.
The other examples were much the same. - JamesJM