What supporting documentation should I include when I file the business privilege and mercantile tax return?

Include a copy of any Federal documentation such as Schedule C (Form 1040), Schedule E (Form 1040) , Form 1120 (S-Corp), Form 1065, or any like form used to file with the IRS. If your business does not have these forms, then provide other documentation used to determine gross receipts (such as your sales spreadsheet).