Double taxation & gross receipts tax

Why am I paying taxes twice on the same income?

You're not!

Income taxes and gross receipts taxes are different taxes. Income tax is paid on the profit a business earns (sales less business expenses); gross receipts tax is paid on the sale amount.

I earn commissions on sales on which the company I represent pays gross receipts tax. Isn't that tax collected twice?

Maybe

Commissions involve 2 separate transactions which both of which may be subject to gross receipts tax. The first is the sale of a product or service on which the seller must determine whether the sale is taxable. The second there is the commission paid to the sales representative for facilitating the sale. Note: If the sale is not taxable, then the commission is also deductible.