Hello. Someone asked this question on the forum, and I'm copy-pasted it here to ask for assistance, as I'm experiencing the same issue.
"Upwork keeps telling me that my tax information is not complete. I have filled all my tax information except the form that requires me to input my Tax Identification Number(TIN). I don't have a tax Identification number because the way it works in my country Nigeria, you need to have a registered business of your own, or be an employee with an employee's ID card, for you to get a tax Identification number. None of which I have, neither am Upwork's employee. So, how can I go about this issue as I can't withdraw funds?"
