A one day civil service strike over pay and job cuts has been scheduled to coincide with the final deadline for tax returns.
If the strike, which is subject to a ballot of 280,000 members of the Public and Commercial Services Union, goes ahead on January 31, it could disrupt the processing of the tax returns.
The ballot is the culmination of discontent over a number of issues including: privatisation of services, job cuts and pay.
A spokesman for the PCS said that further industrial action may take place targeting specific departments.
Separately, the Inland Revenue & Customs has denied reports that it offers cash bonuses to tax inspectors to help increase the amount of unpaid tax that is reclaimed. It claims that it takes into account a number of criteria when paying staff bonuses.