Between May 17 and June 27, 2018 the branches in Beccles, Thetford, Gorleston, Holt, Hunstanton and North Walsham will close following a decision by parent company RBS to shut 197 NatWest outlets nationally.
The affected branches are due to close in six months' time, "in order to ensure our customers have time to consider the right banking options for them".
An RBS spokesperson said: "As customers change the way they bank with us, we must change the way that we serve them and this means that some branches will have to close".
Unite, the UK's largest union, representing staff across RBS, accused the taxpayer backed bank of decimating its branch network and betraying communities.
Transactions in NatWest Whitby Yorksbranch have reduced by 38% since 2012 with now only 74 customers visiting the branch on a weekly basis.
Shares of Royal Bank of Scotland Group (LON RBS) traded up GBX 10.40 ($0.14) during trading on Wednesday, hitting GBX 281.60 ($3.77). We realise this is hard news for our colleagues and we are doing everything we can to support those affected. The situation has sparked fears that some communities will be left without bank branches, with many still unfamiliar with online processes. "Now serious questions need to be asked about whether these closures mark the end of branch network banking", said Unite's Rob MacGregor.
But the trend has prompted fears for communities being left without a bank in their town and those unfamiliar with the developments of the digital age being cut adrift.
"The sheer scale of this latest round of branch closures is savage".
In a statement Natwest said it was "communicating with our customers affected by the closure and proactively contacting vulnerable customers and regular branch users".
The announcement comes after the Government last week disclosed plans to dispose of about two-thirds of its stake in RBS, selling off about £15bn a year over five years from 2018/19.
But it still expects to report an annual loss for 2017 - its tenth in succession - as it faces an imminent fine from the US Department of Justice over its sale of toxic mortgage bonds in the run-up to the crisis.
In a separate announcement, the Yorkshire Building Society has announced that its Norwich & Peterborough branch in Hampton will close next March.