This section of the forum is for discussing the business and finance issues of the t-shirt industry. Which business structure to use (sole proprietor, LLC, S Corp, etc), how to handle billing, where to register your business and get the proper licensing, etc.
You probably still need to register with the sales tax people. Two reasons for this. First, you are a retailer and probably need to register just for that reason. Sales tax remittance forms gererally ask for Total Sales - Less Exempt Sales to give the Total Taxable Sales. In your case if all you ever sell is clothing your total sales and exempt sales would balance out to Zero, but you should still submit the form.
Second reason is that many suppliers will want your Sales Tax Exemption number in order to sell you at wholesale. Not all, but some.
Better to register and spend 5 minutes a quarter submitting an online form saying you owe nothing than to have them come looking for you.
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tax in Pennsylvania 
