Is interest income earned in an SCorp's bank account included in the calculation of an SCorp's basis as an addition?
The calculation should include separately stated items.
See https://www.irs.gov/instructions/i1120ssk#idm140355075208448
here's a worksheet you can use
https://www.thetaxbook.com/updates/TheTaxBook/Client%20Tax%20Tools/S_Corporation_Shareholders_Adjusted_Basis_Worksheet.pdf