Apportionment

Updated October 2024

This guide is intended to help businesses with apportionable income understand their tax reporting responsibilities in the state of Washington. The information in this guide is general in nature and does not replace or substitute Washington laws or rules.

For more information or to get answers to specific tax questions, you may request a ruling at RulingsDOR@dor.wa.gov.

For help with reporting or questions about payments, see our My DOR Help Topic.

Check out our new Annual Reconciliation of Apportionable Income video