Customers from Lloyds, Halifax and Bank of Scotland will be able to use services in any branch as part of a shake-up that has sparked fears of further site closures across the UK.
Lloyds Banking Group, which owns all three banking brands and is the UK's biggest moneylender, said the move would give customers more choice and flexibility.
A date has not been confirmed for when the changes will come into effect, but concerns have been raised by unions that the move could lead to more branch closures and job cuts.
The banking group said its latest decision would enable Lloyds, Halifax, and Bank of Scotland customers the option to use branches of any brand for in-person banking, as well as "apps, mobile messaging, and telephone services".
"As with many industries, most of our customers are moving to mobile and online banking because it is faster, easier, and more convenient," a statement added.
A major overhaul of the business in 2022 saw Lloyds close dozens of its branches and cut hundreds of staff due to more people banking online.
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