Small businesses can have varying deadlines depending on the type of company, the state the taxes are filed in, and other factors. Consider an extension Because of some pending tax legislation in Congress this year, Mitch Gerstein, senior tax adviser at accounting firm Isdaner & Co., said it might be a good idea to file for an extension. The bonus depreciation allowance was designed to spur capital purchases and it let businesses write off 100% of certain new and used assets in 2022.