I believe you can only file certain forms, and even that varies based on whether you're filing for other people, whether you're self-employed, whether you make

I believe you can only file certain forms, and even that varies based on whether you're filing for other people, whether you're self-employed, whether you make over $10M, etc. (https://www.irs.gov/e-file-providers/e-file-for-business-and-self-employed-taxpayers https://www.irs.gov/e-file-providers/e-file-for-business-and...) If you want to write e-file-enabled software for others I think you need to become an Authorized e-file Provider (https://www.irs.gov/e-file-providers/become-an-authorized-e-file-provider https://www.irs.gov/e-file-providers/become-an-authorized-e-...)