Invest in Innovative Small Businesses Act This bill amends the Internal Revenue Code to allow a new business-related tax credit equal to 25% of the equity investments made by a qualified investor in a domestic corporation or partnership that: is a small business, has its headquarters in the United States, is engaged in a specified high technology trade or business, has been in existence for less than 5 years, employs fewer than 100 full-time employees, has more than 50% of its employees performing substantially all of their services in the United States, and has certain equity investments designated for the purposes of this bill that do not exceed specified amounts. The bill limits the allowable amount of such credit to the excess of the sum of regular tax liability, plus the tax under provisions regarding the alternative minimum tax, over the sum of specified tax credits allowed for the year. It also imposes an overall limitation on such credit of $500 million for each of calendar years 2018 through 2022.