The "Investing in American Workers Act" introduces a new employer-provided worker training credit within the Internal Revenue Code. This credit is designed to incentivize businesses to invest in the skills development of their workforce, specifically targeting non-highly compensated employees. It generally provides a credit equal to 20 percent of the increase in qualified training expenditures compared to the average of the three preceding taxable years. To qualify for the credit, training must lead to a recognized postsecondary credential and be delivered through specific programs, including registered apprenticeships, Workforce Innovation and Opportunity Act (WIOA) listed services, or programs offered by community colleges, labor organizations, or industry partnerships. This ensures that the training is structured and leads to verifiable skills. The bill also includes a special provision for new training initiatives, offering a 10 percent credit on current year expenditures if there were no qualified training expenses in the prior three years. A significant feature of this legislation is the option for qualified small businesses (those with less than $5 million in gross receipts) and qualified tax-exempt organizations to elect to apply a portion of the credit, up to $250,000, against their payroll tax liability. This provision aims to make the credit accessible and beneficial even to entities that may not have sufficient income tax liability to fully utilize a traditional tax credit. The Secretary of the Treasury is directed to provide simplified filing methods for these small businesses. Furthermore, the bill mandates the Secretary of Labor, in consultation with the Secretary of the Treasury, to issue guidance on the definition of a "recognized postsecondary credential" within one year of enactment. The Treasury Secretary is also tasked with prescribing regulations for the payroll tax election, including rules for preventing avoidance, minimizing compliance burdens, and requiring the collection and reporting of demographic information (race, ethnicity, and gender) of individuals receiving training.