Generally N. Ireland/UK residents who have earnings that arise outside of the UK are subject to self-assessment by Revenue in the north.  They are given a credit or relief in respect of any Irish income tax because of the double taxation agreement between the Republic and the UK.  There may or may not be a balance of UK income tax to pay.  Our information materials in the area of tax are not sufficiently detailed to be able to advise you if 'government' employees in the Republic are exempt from the above. I would suggest you contact Revenue in the north and ask for clarification from their technical support team, phone 08453021481, you should be able to do so confidentially.