HSBC is reviewing its trail commission payments from pension savers after a Financial Ombudsman Service ruling ordered it to refund a client.
In August, the bank was forced to repay the trail commission to a client, Mr J, because it was not providing ongoing advice.
Experts have warned the case could open a “huge can of worms” because many other advisers and banks are in similar positions.
They argue some trail commission was not designed to pay for ongoing advice but to act as initial commission spread over a longer period.
A HSBC spokesman says: “The circumstances surrounding this case are very specific, but as always with FOS decisions, we will review our portfolio to identify if there are any other customers in the same situation.”