Green Bus Tax Credit Act of 2019 This bill allows a manufacturer a zero-emission bus tax credit. The credit is equal to 10% of the sales price of a zero-emission heavy vehicle. The credit only applies to the first $1 million of a vehicle's sales price. The bill defines "zero-emission heavy vehicle" as a motor vehicle that has a gross vehicle weight rating of not less than 14,000 pounds, is not powered or charged by an internal combustion engine, and is propelled solely by an electric motor that draws electricity from a battery or fuel cell.