State Income Tax Apportionment Calculator: Single Sales Factor vs Three Factor
Where a manufacturer makes goods and where it sells them can be very different states. Apportionment decides how much of your income each state may tax. This tool compares the two most common formulas.
Your numbers
Use the state's sourcing rules, which differ for goods and services.
Your results
States differ on weighting, throwback, market-based sourcing and combined reporting. This is a simplified two-formula comparison for planning, not a return computation.
State tax vs sales sourced to the state
Sweeps Sales sourced to this state from 0 to 40000000, holding your other inputs fixed.
Sales by ship-to state from your ERP
Optional: a read-only report of sales by ship-to state for apportionment support.
Optional. The tool and every export work without this. No spam.
How to use it
Enter apportionable income, total sales and the sales sourced to the state under that state's rules. Add the state's share of your payroll and property to see the three-factor result. The calculator shows the sales factor, the three-factor percentage and the tax each would produce. Use the sweep to see how state tax moves as sales sourced there grow, which helps when you open a new distribution channel or move a plant.
The method
Single sales factor apportionment assigns income to a state in proportion to its share of sales. The three-factor formula averages the sales, payroll and property factors, each weighted equally in this model. Many states have moved toward single sales factor, and some double-weight sales instead. A manufacturer with large plants in a state but most customers elsewhere pays more under three-factor and less under single sales.
- Sales factor = state sales / total sales
- Three-factor = average of sales, payroll and property factors
- State tax = income x apportionment x rate
- Check your state for weighting, throwback and sourcing rules
Worked example and common mistakes
With 5,000,000 of income, 6,000,000 of 40,000,000 sales in the state (15 percent), 55 percent payroll and 50 percent property, three-factor is 40 percent. At a 6 percent rate, single sales tax is 45,000 and three-factor is 120,000, a 75,000 difference. Mistakes include using billing rather than shipping destination, ignoring throwback rules, forgetting that some states tax gross receipts or margin rather than income, and treating Texas franchise tax as income tax.
Sales sourcing data in the ERP
Apportionment needs sales by ship-to state, payroll by work location and property by site. ERP sales order ship-to addresses, HR location codes and fixed asset locations are the typical sources. Reconcile them to the trial balance before year end to avoid late scrambles.
Frequently Asked Questions
Which states use single sales factor?
A large and growing group of states do, but the list changes, and some apply it only to manufacturers or to certain industries. Check the current statute or your adviser rather than relying on a fixed list.
What is throwback?
A throwback rule assigns sales of goods shipped from a state to customers in a state where you are not taxable back to the origin state. It can raise the origin state's sales factor and tax.
Do I need nexus to use this?
Apportionment only matters in states where you have nexus. Economic nexus thresholds for income tax and public law restrictions on solicitation of orders differ from sales tax thresholds, so assess each tax type separately.
Does this cover Texas franchise tax?
No. Texas franchise tax is a margin tax with its own apportionment on gross receipts and different base calculations. Use this tool for income-based states and a Texas-specific tool for franchise tax.
We can help build a read-only report that totals sales by ship-to state and payroll by site from your ERP and HR system.
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