Taxes & Entities

State Tax Apportionment

Two questions decide a multistate tax bill: which states may tax you, and what share of your income each one claims. The second is arithmetic — and it runs on inputs you control.

  • Advanced
  • 9 min total
  • 13 chapters

What decision this helps you make: How much of your company's income each state gets to tax, and which of your own operating choices move that number.

What this topic is

A company doing business in several states does not have separate income in each one. It has a single pool of income, and every state with a claim applies a formula to take a share. Apportionment is that formula — historically an average of your property, payroll, and sales shares in the state; increasingly, just your sales share.

Why it matters

Nothing guarantees the shares add up to 100 percent. States use different formulas and different rules for where a sale happens, so the same dollar of income can be claimed twice or by nobody. The formula also runs on inputs you decide: where people work, where property sits, and how service revenue is sourced.

Who should learn it

Owners and finance leads at companies selling into multiple states, anyone with remote employees, and buyers running tax diligence on a multistate seller.

What you will understand

  • The two-step: nexus first, then apportionment — they are different questions
  • The three factors, and why sales swallowed the other two
  • Cost-of-performance versus market-based sourcing, and the double-tax gap between them
  • Throwback rules and Public Law 86-272 — why "no nexus there" is not always "no tax"

Prerequisites

Common misconception

"We pay tax where we are located." Location stopped being the test. A state can require a return based on your sales into it alone, and its formula may claim a share of your income based on where your customers are rather than where the work was done. Meanwhile the state where you do have property and people can pull those same sales back into its own numerator precisely because the other state cannot tax them.