December 13, 2018 Tax reform changes the cash method of accounting for some businesses. Here’s how the rules changed. The law: Allows small business taxpayers with average annual gross receipts of $25 million or less in the prior three-year period to use the cash method of accounting. Exempts small business taxpayers from certain accounting rules for inventories, cost capitalization and long-term contracts. Allows more small business taxpayers to use this cash method after December 31, 2017.