US SMALL-BUSINESS GUIDE
Calculate sales tax without confusing tax with revenue
A calculator can split the numbers, but it cannot decide where a sale is taxable or which state and local rules apply. Use this workflow to choose defensible inputs.
1. Confirm the obligation before choosing a rate
US state and local tax obligations vary by location and business activity. Start with the relevant state tax authority rather than a general rate table. The IRS maintains a directory of state government websites, while the Small Business Administration recommends checking state and local governments for the obligations that apply to the business.
2. Use the combined rate that applies to the transaction
A state rate alone may not capture county, city or district tax. Confirm the transaction’s sourcing location, whether the product or service is taxable and any customer exemption before entering the combined rate. Tool IQ deliberately asks you for the rate instead of pretending one rate fits an entire state.
3. Keep collected sales tax out of operating revenue
For federal small-business reporting, IRS Publication 334 says sales taxes imposed on the buyer that a business collects and pays over should not be included in gross receipts or sales. In management reports, separating collected tax also gives a clearer view of revenue, margin and cash reserved for remittance.
4. Calculate in the right direction
Use the Sales Tax Calculator when you know the pre-tax subtotal. Use the Reverse Sales Tax Calculator when a tax-inclusive total must be separated into subtotal and tax. Then carry only the pre-tax revenue into the Profit Margin Calculator.
Worked example
At an entered combined rate of 8.25%, a $100 taxable subtotal produces $8.25 of sales tax and a $108.25 customer total. Reversing $108.25 at the same rate returns a $100 subtotal. The example demonstrates the arithmetic only; it does not establish that 8.25% is the correct rate for a particular sale.
Official starting points
- US Small Business Administration: Pay taxes
- IRS: State government websites
- IRS Publication 334: Tax Guide for Small Business
Published and checked 27 July 2026. This planning guide is not tax or legal advice. Confirm current rules with the relevant state and local authorities.