Retail giant Marks & Spencer will terminate its current account offering this summer - with 29 concessions to also close.
The chain, which has 3million banking customer in the UK, said its Monthly Saver savings account will also shut in August along with in-store counters, as it switches its focus to digital banking.
M&S Bank said it will start contacting current account customers from Wednesday, making them aware of the changes and their options.
This will include switching to another lender using the seven-day Current Account Switch Service or closing their account completely.
Either way, all accounts will be shut in August - or sooner if the customer has a zero balance. Overdraft charges and outstanding fees must still be repaid.
Marks & Spencer Bank's current accounts are currently underwritten by HSBC, which it partnered with in 2010, four years before branching into the current accounts market.
Over the years it's won new customers over with £100 M&S gift cards and £80 vouchers for the most loyal shoppers.
It also allowed customers to also earn loyalty points on debit card spends - equivalent to one point for every £1 spent in-store and online at M&S.
The company today said in-store travel money counters, which are located in over 100 M&S branches, are unaffected.
It did not say how many workers would be affected as a result of the closures, however a spokeswoman confirmed staff have today entered consultation.
The bank said the next stage of its transformation programme will be to focus on credit cards and rewards with plans to merge further with its Sparks Card.
However, from summer 2021, all M&S Bank services will be available online and over the phone only.
Paul Spencer, CEO, M&S Bank, said: "As we adapt to meet the changing needs of our customers, and we deliver some new - more digitally-focused products and services – it does regrettably mean we will move away from branch-based servicing and the 29-in-store bank branches and associated current account will close this summer.
"We're now firmly focused on supporting both our customers and colleagues through this change, and the delivery of our transformation plans, which will create new and rewarding payment solutions for M&S shoppers, both in-store and online."
The bank said it plans to launch a new reward credit card offering and a digital payment solution for Sparks customers later this year.
It will continue to offer its existing range of general insurance, savings and loan products.
Kirsty Ward, director of bank and services, at M&S, said: "M&S was an early pioneer in retail financial services, and the rapid transformation in how we spend, borrow, save and protect has never been more exciting.
"We are striving to bring our customers the very best financial products that meet their needs today and in the future - and our priority, as set out today, is making it even easier and more rewarding to buy the things they love from us."
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My account is closing - what are my options?
Customers have two options ahead of the planned closures in August.
The first is to use the free Current Account Switch Service (CASS) to switch to an existing current account or a new one entirely.
The CASS service will ensure all of your direct debits and incoming payments are switched across, too.
The second option is to close your account ahead of the forced closures.
M&S Bank said: "Once your account has a zero balance we will automatically close it in August and write to you to confirm."
If you already have a zero balance and want to close your account sooner, you can do so here.
Your account can only be closed with a zero balance. M&S Bank said it will contact customers about any ongoing outstanding debt after August.
Bear in mind that direct debts and any payment plans registered to the account will be automatically cancelled when the account closes. This could mean your payments bounce - which could risk a mark on your credit file.
M&S said once it's closed your account, it will email you a copy of your transaction history covering the past five years within 10 working days. Make sure they have the correct email address on record to enable this.
What about M&S Monthly Saver customers?
The bank is also closing its Monthly Saver savings account.
However it said it will ensure customers receive the full payout they would have earned if the account had remained open for the full 12 month term.
"If your account is closed before maturity, we'll assume a maximum contribution of £250 has been made in each remaining month to calculate your interest," the bank said.
