Washington (WA) Corporate Tax Rate, Economic Nexus, Apportionment & IRC §174 Conformity Guide (2025/2026)

1. How Washington Apportionment & Economic Nexus Impact ASC 740 Tax Provisions

For multi-state C-Corporations and SaaS companies selling into Washington (WA), exceeding $100,000 in annual WA-sourced receipts (or maintaining remote W-2 employees inside the state) establishes nexus under Washington's B&O Gross Receipts Tax (1.5%). Under 100% Gross Receipts apportionment and Market-Based (Benefit Received) rules, SaaS subscription revenue is sourced to Washington based on where the customer receives the benefit of the software.

2. Washington Federal-to-State Tax Base Modifications (§174 R&D & §168(k) Bonus Depreciation)

• IRC §174 R&D Capitalization Rule in Washington: Washington DECOUPLES from federal TCJA IRC §174 capitalization! Taxpayers filing in Washington may deduct 100% of current-year domestic R&D expenses on their WA return via a state subtraction modification—dramatically lowering WA taxable income compared to Federal Form 1120.
• IRC §168(k) Bonus Depreciation Rule in Washington: Washington decouples from federal IRC §168(k) bonus depreciation. Corporate taxpayers must add back federal bonus depreciation on the WA return and track a separate state depreciation basis rollforward.
• Pass-Through Entity Tax (PTET) Election: Washington does not currently levy a traditional individual income tax with a corresponding PTET election.