The hook
“If a foreign employee is leaving Singapore and payroll treats IR21 as optional cleanup, the risk starts before the last payslip.”
IRAS says employers generally need to file Form IR21 at least one month before a non-Singapore citizen employee ceases employment, goes on an overseas posting, or leaves Singapore for more than three months. The same guidance also points employers to withhold monies due once the departure trigger is live. That makes tax clearance an operational process, not a casual end-of-employment form.
The takeaway
The practical Singapore question is usually not whether the employee remembers tax, but whether the employer ran clearance on time.