Santander will close around a fifth of its branches by the end of August.
The bank said 111 branches will shut in response to customers increasingly making transactions online.
Branch transactions fell by a third over the two years before the pandemic and declined by a further 50 per cent in 2020, Santander said.
Mobile and online transactions have been growing by 20 per cent each year, with almost two thirds of transactions now digital.
Most of the branches being closed are less than three miles from another Santander branch, and the furthest is five miles.
The lender said it hopes said it expects to find alternative roles for a significant number of staff affected by the announcement.
The Communication Workers Union said it had reached an agreement with Santander on new ways of working which will preserve jobs and avoid compulsory redundancies.
National officer Sally Bridge said: “Recent membership surveys have indicated a desire from a large majority of those currently working from home for flexibility to continue after the pandemic, and this agreement achieves that for the majority of employees affected by these changes.
“Ultimately, however, faced with the proposals of site closures and consolidations, the deal we’ve negotiated has avoided compulsory redundancies by giving individuals genuine options, crucially protecting our most vulnerable members for whom dual location arrangements were not suitable on account of their exceptional circumstances.
“Santander deserves credit for recognising its responsibilities to its employees and I hope other employers follow the moral lead the bank has taken in what is likely to be one of the first of many far-reaching corporate readjustments to the post-Covid world of work.”