If i may asked when did you start having to provide this tax number and which bank ?
I have updated my passport many time in the past ( when passport was for 5 years) & never had to provide this .
I did not step into China from late 2019 to Nov 2023, due to Covid. During this period,
(a) my BOC-Shanghai & ICBC-Quanzhou bank a/c were frozen (probably due to expiry of passport validity date)
(b) my internet banking access to above banks were also frozen (probably due to same reason)
(c) my internet banking tokens (U 盾) also ran out of battery & cannot be recharged
Nov 2023:
Tried to update my passport details, plus re-activate my frozen bank a/c & internet banking access & replaced the tokens when I was in Beijing/ Tianjin. Went to BOC-Beijing 朝阳门支行 & ICBC-Tianjin (can't remember which branch, but should be a 支行 around 解放路). I filled up many Forms, & I recalled the TIN (Tax Identification No.) was in one of the Forms. In the end, I only managed to complete (a) & (b) for both bank ac. For (c), the applications were un-successful. I was told that it's better to apply at the 开户行 (i.e. Shanghai & Quanzhou).
May 2024:
Applied successfully for BOC Banking App (手机银行) at BOC-Xiamen. I was told that with this application, my daily ATM transaction limit would be reduced to RMB1,000. I could not recall whether TIN was asked during the application.
Sep 2024:
Renewed my passport in Aug 2024, so updated my passport particulars at both banks in Quanzhou during my China trip in Sep 2024. I could not recall whether TIN was asked during the update.
After every update/ application, the banks do provide the carbon hardcopies of the system-printed Forms, indicating the updates/ applications made. However, I left these Forms in China, so can't check them now.
But my point is: it's perfectly normal for banks to require your Tax Residency info (i.e. which country, & the TIN) in their system. Under what circumstances would the bank trigger to ask you for an update - I don't know. But I recall during Covid, whenever I logged into internet banking (before it was frozen), I was prompted the message to update my Tax Residency.
If they do not ask, it could be because their system assumes that the info is still valid.
But if they ever ask, then the correct answer should be your NRIC No (which is the IRAS Tax Ref No) if you are Singaporean.