Steve1960 is correct.
If you don't pay your annual tax due, then your ex-employer is on the hook for it. That's why they withhold the final month pending the calculation of any outstanding liability, that's meant to leave them more than covered. In theory you get the net back later.
Long ago I left an employee here, and they did this. As it happened I transferred back to my 'home branch' of the same company. I forgot about having the final month withheld, until maybe a year+ later hearing via HR that the SG branch had a further net-liability for me from IRAS and that I had to pay it.
Initially I refused to accept the liability 'arising from the error in HRs calculation at the time of departure'. But you can imagine the '['Cannot compute'] - This is the government you know!' response that got. I strung it out as long as I could 3+ years, until it threatened becoming a perpetual issue for me with local HR.
So I paid it off, at maybe $100 a month. By then I was in the US, and had personalised 'checks' with a fisherman's design... like this...
http://www.purechecks.com/fishermens-ch ... d-dunleavy - So on the sharks and fish I'd artisticly enhance (by hand/pen) them with protruding fangs, menacing eyes, and so on. Together with a few pinholes through the machine-readable numbers at the bottom. So I begrudgingly eventually settles that debt, but at the same time had some bitter fun doing so...
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Edit to add: Before this gets misquoted/misrepresented on some other local forum.
The local SGn company had
settled my liability in full, when due, with SG-IRAS.
The outstanding issue as described was solely between me and SG-HR. My issue being that they, together with their external accountants, had woefully miscalculated something that should have been very simple... and then took a year/years to follow it up. My opening position was that that they should hence write it off ... but, that's not the SGn way ...
