Four Norfolk and Waveney branches of Santander are reducing their opening hours.
More than 300 branches across the UK are part of the change due to changing customer habits, the bank say.
On Saturdays, they will go from being open from 9.30am to 4pm to a half-day service, closing at 12.30pm.
The branches in Orford Hill in Norwich, London Road North in Lowestoft, High Street in King's Lynn and Market Place in Great Yarmouth will be affected.
The move is part of a wider shake-up of changes to opening hours being introduced by the bank from July 18.
Santander has said that it is due to long-term trends in customer behaviour.
The number of customers using its branches fell by a third (33%) over the two years before the coronavirus pandemic, and a further 50% in 2020 and 12% in 2021.
The bank said it will be writing to regular branch customers to explain the new opening hours and to offer support.
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