Approximately 680 jobs will be cut, according to RBS. In England and Wales the number of NatWest branches will fall to 655.
A spokeswoman said more people were choosing to bank online, and that customers could also do some bank at post office branches.
The closures will result in around 680 redundancies, which it hopes will be largely achieved on a voluntary basis.
"We know that not all of our customers are comfortable or familiar with using online or mobile banking, so we have created a new specialist taskforce of NatWest TechXperts who will be dedicated to supporting our customers with training and support with digital skills until the branch closes". "Over 5 million customers now use our mobile banking app and one in five only bank with us digitally".
Trade union Unite called the cuts "savage", with national officer Rob MacGregor saying: "This announcement will forever change the face of banking in this country resulting in over a 1,000 staff losing their jobs and hundreds of High Streets without any banking facilities". The situation has sparked fears that some communities will be left without bank branches, with many still unfamiliar with online processes.
In March RBS had already announced the closure of 158 branches with the loss of 500 jobs.
'We provide our customers with more ways to bank than ever before, ' she said.
Last week, the Government disclosed 2018/19 plans to sell around two-thirds of its RBS stake, which would equate to about £15bn over five years.
On Thursday, RBS announced the closure of its so-called "bad bank" - the unit set up to dispose of large chunks of unwanted assets following its £45bn taxpayer rescue - marking another chapter in its recovery.
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