Jason Benham, 37, who worked at the Lloyds TSB branch in Mildenhall, Suffolk, was sentenced at Ipswich Crown Court after admitting a series of charges of fraud and obtaining money by deception charges.
At the trial, prosecutor Rosalind Jones told the court that transactions were so complex investigators had not been able to calculate the exact total missing. It was estimated it could have been as high as £700,000.
She said Benham had committed new frauds to cover up previous ones. He had persuaded one couple to take out a series of new loans to cover previous ones. With each new loan, he took between £6,000 and £10,000 for himself.
The scam unravelled when a customer complained his endowment payout had not been used to reduce his debt with the bank.
Judge John Devaux said Benham had “groomed” customers who used him as their sole point of contact with the bank and he abused this trust.