Most larger genuine wholesalers may require a tax id to indicate you are a legit trading entity. As a general rule where a tax id is not required to purchase, they are not genuine wholesalers, just a middle men businesses.......and that of course means that you will be paying a premium price, not genuine wholesale.
In Australia you would require what is called an ABN, and you would need to apply through the ATO to get one, however they are free. If you are not in Oz, then just contact your local business licensing authourity for assistance.