Generally, when your non-Singapore Citizen employee ceases employment with you in Singapore, goes on an overseas posting or plans to leave Singapore for more than three months, you must notify IRAS at least one month in advance and withhold all monies due to the employee from the date you are aware of his impending cessation of employment or departure from Singapore. This process is known as tax clearance and it applies to all work pass holders including Personalised Employment Pass (PEP) holders.
