The Bureau of Immigration has recently issued JHM-2019-009, entitled "Taxpayer Identification Number in Visa and Permit Applications" ("TIN Rules").
The TIN Rules may be found here.
What the TIN Rules say
Under the TIN Rules, all applications for non-immigrant visas and other work-related visas and permits must be accompanied by a copy of the foreign national's Taxpayer Identification Number (TIN) card or any proof of TIN.
Actions to consider / Conclusion
Ensure that all future application for work visas / permits are accompanied by corresponding proof that the applicant has been issued a TIN.