You need a TIN number in order to pay tax.
no need to pay tax if your annual TAXABLE income is more than 1.2 mil.
service provider FC income is not taxable.
Dont panic. Wait until you get enough to pay tax.
Just start working on the new company on time.
Take your remaining leaves, if not enough then take no pay leaves.
If both companies allow work from home, then you can do both for a couple of months (this is what we do normally)