Why must I pay taxes twice on the same income?

You are not actually paying taxes twice on the same income. Income taxes and gross receipts taxes are different tax programs

 

Why are commissions taxed? Isn’t that double taxation?

 

Taxes on commissions paid to independent contractors are taxes on one kind of transaction, the percentage or fee charged for the performance of a service in New Mexico. The tax on gross receipts from the underlying transaction, i.e., the basic sale or lease on which the commission is based, is another type of transaction. This does not result in double tax on a single sale or lease, but rather tax is paid on two separate transactions. When the underlying transaction itself is not taxable, New Mexico allows a deduction for the commission earned.