Clarifying the scope of the investment income business and occupation tax deduction.

This bill clarifies which investment income businesses can deduct when paying Washington's business and occupation tax. It defines "investment income" broadly to include dividends, interest from related entities (with a 5% gross receipts cap), and standard investments like stocks and bonds, while explicitly excluding banking, lending, factoring, and loan income not meeting the 5% rule. The changes apply retroactively to past tax periods but do not create new refund rights for taxes paid before the bill's effective date. It directly affects businesses filing B&O tax returns with investment income, providing certainty after recent court disputes over tax deductibility.