Some long-standing accounts received very large cheques (it was the 90s, so yes, cheques).

The FI gave the customers the choice to either return the cheques or have future interest payments withheld. Surprisingly the vast majority simply returned the cheques.

We had to write additional code to clawback the interest on the other accounts. I doubt if the FI would have had any recourse if people had just closed their accounts and kept the cheque but to the best of my knowledge nobody did.