HM Revenue and Customs (HMRC) has announced a voluntary redundancy scheme affecting staff in four of its offices in NI.
The offices affected are in Enniskillen, Londonderry, Newry and Belfast.
An HMRC spokesperson said the redundancies were necessary as more customers choose to do business with them online.
The number of staff eligible to apply for redundancy is 24 in Enniskillen, County Fermanagh; 77 in Londonderry; 134 in Newry, County Down, and five in Belfast.
The HMRC spokesperson said: "An increasing number of customers are choosing to do business with us through our online services, which has reduced our need for physical sites.
"This change has seen the nature of our work shift away from the mass processing work of the past to the more specialist, but less labour-intensive, roles required in effective policing of the tax system.
"As a result some areas of our work do not require as many staff."
The spokesperson added: "We are not closing any offices today."
Sinn FÃ©in MPs Conor Murphy and Michelle Gildernew, along with SDLP MP Mark Durkan, are to travel to Westminster to press the UK government to reconsider the job losses.
Mr Murphy, MP for Newry and Armagh, said: "This has come out of the blue for the workers.
"They have been told they have to agree to a voluntary exit scheme by 18 December, and are adamant there is no opportunity for redeployment."
Almost 250 civil service jobs could be lost in Northern Ireland.