For a SCH C business, your sales taxes isn't entered in the business section of the TTX program. I think it's rather odd myself with the Self Employed version. But if you'll look under the Deductions & Credits tab and under the Estimates and Other Taxes Paid header, you'll see a section labeled "Sales Tax". That's where it belongs.
Some say that's sales tax for things you purchased and paid sales tax on. Really not so. Sales tax, is sales tax. Period. However, entering it on the SCH C can potentially reduce your SE tax, which also has the potential to reduce the amount of retirement contributions you can make. It just depends on the amount I guess.
