Single Sales Factor vs Three-Factor State Apportionment

The traditional apportionment formula averages three ratios: the share of your property in the state, the share of your payroll in the state, and the share of your sales in the state, each compared to your totals everywhere. A company with a warehouse and staff concentrated in its home state but selling nationally used to get taxed more heavily there because two of the three factors, property and payroll, were anchored to that state. Only a handful of states still use a meaningfully weighted three-factor approach today.

Most states have shifted to weighting sales alone, or nearly alone, in the apportionment formula. The logic from the state's side is straightforward: a formula that includes property and payroll can discourage a company from building facilities or hiring locally, since doing so increases the state's claim on your income. A sales-only formula taxes you based on where your customers are, not where your headquarters or warehouse happens to sit, which is friendlier to companies with a real physical presence in the state and tougher on companies that sell heavily into a state from somewhere else entirely.

Say your company has all of its property and payroll in State A but sells a third of its revenue into State B with no physical presence there at all: under a three-factor formula, State B's apportioned share of your income stays small because two of the three factors are zero there, while under a single sales factor formula, State B's share tracks your actual sales percentage into that state, which can be a much larger number. That's the shift in a sentence: single sales factor moves the tax burden toward states where you sell, away from states where you merely operate.

For companies selling services or intangibles rather than goods, states also had to decide where a sale is even sourced. The older approach sourced a service sale to wherever the cost of performing it was incurred, usually your own location. Most states with a single sales factor have paired it with market-based sourcing instead, which sources the sale to where the customer received the benefit of the service. That single change can dramatically shift which states you owe tax to if your service delivery team sits in one state but your customers are spread nationally.

Apportionment only matters once you actually have nexus, a taxable connection, with a state. Physical nexus from an office, warehouse or employee is the obvious kind, but many states also apply economic nexus for income and franchise taxes based on sales volume into the state, with no physical presence required, although federal law (P.L. 86-272) protects some sales of tangible goods limited to solicitation. If you've never checked whether your sales into a state cross its economic nexus threshold, you may owe an apportioned share of income there that you've never filed for, and that exposure can be larger than a small formula error in a state where you're already registered.

Apportionment rules, factor weighting and sourcing methods vary by state and change periodically, so don't assume last year's method still applies or that every state you operate in uses the same formula. Before your next filing, confirm with your state tax advisor which formula and sourcing method each state you have nexus in currently uses, whether any of them still apply a throwback rule that pulls an unsourced sale back to your origin state, and whether your revenue mix between goods and services means different sourcing rules apply to different parts of the same year's revenue.

Confirm these points for every state where you file:

• Which apportionment formula the state currently uses and how it weights sales, property and payroll, since these vary by state and change over time.
• How the state sources service and intangible sales, including whether it uses market-based sourcing or the older cost-of-performance approach.
• Whether you have nexus there, including economic nexus created by sales volume with no physical presence.
• How your property, payroll and customer footprint plays out under that formula, so you know where your share of income rises or falls.
• Whether last year's method still applies, verified with a state tax advisor rather than assumed.