Tax office staff across Northern Ireland have walked out early in a protest at sickness policy.
The Public and Commercial Services union (PCS) said members at Revenue and Customs offices will go to work at 10am on Wednesday and take a "mass extended lunch" for two hours from 11.30am.
An HMRC spokeswoman said the service was disappointed at the decision to disrupt the working day over the "simplified" but unchanged sickness policy.
PCS branch secretary Barney Lawn said: "If you have had a clean sick record for 10 years and you had a bout of illness, then you would be facing potential disciplinary procedures which could lead to dismissal."
He claimed medical appointments now must be taken outside working hours. According to Mr Lawn, the measures were introduced in February this year.
In protest union staff will be refusing to work overtime, use private cars for work or "cut corners". The union also said the sickness policy allows managers to exert undue pressure on staff.
Full-time staff at HMRC are entitled to full pay for six months after going off sick, a spokeswoman for the organisation said.
The HMRC spokeswoman said it had not changed its sickness policy, merely simplified it.
She added: "HMRC is disappointed with the decision to disrupt the working day and will do everything it can to maintain services to the public. HMRC will continue to talk to the unions to address their concerns regarding this change.
"The wellbeing of our staff is of paramount importance, however HMRC's attendance record must be tackled urgently in the interests of both staff and customers."