Are you going to be using this 'supplier' as a drop-shipper (they provide the goods and ship to your customers)? [Saad] YES
A business who is charging sales tax to the end buyer does not pay sales tax to it's supplier. [Saad] Agreed, I dont.
You provide your tax ID (given to you by your state) to the supplier. [Saad] Agreed, I do same.
BUT do not confuse that with using a supplier who remits the BUYER'S taxes to various states (plus TX), as part of your agreement.
IF YOU are in charge of remitting taxes:
You charge sales tax to whichever states the supplier has an entity in, often warehouses in several states.
You need to know what tax is owed for each state.
IF THEY remit the taxes:
You collect it and remit it to the supplier, and they remit it to each state.
[Saad] By looking at above of your explanation, when my SUPPLIER is drop shipping to an end customer who is in same state of SUPPLIER or his WAREHOUSE then either SUPPLIER can remit the Sales Taxes to that state or I can.
So my initial question where MY SUPPLIER is sending good from NJ to NJ and charging Sales Tax on invoice to me, I have to charge same from my Customer.
Why it was trouble for me is, Customer bought 10 items from me which I was able to arrange from 4 different suppliers 3 of those doesn't exists in NJ and didn't change Sales Tax but 1 has Warehouse in NJ charged me Sales Tax for that drop-ship.
I should charge my customer sales tax for 2 of 10 items here which were sent to them from within NJ.