No, you can't do that. Because of the common ownership, section 414(c) of the tax code requires that these businesses be treated as a single employer for the purpose of a retirement plan. Without this requirement, compensation to make a SEP contribution could be manufactured by one of the individual's sole proprietorships selling services to another, reporting the income on the Schedule C of the selling business and the expense on the Schedule C of the purchasing business.
TurboTax properly aggregates the profit and loss from these multiple businesses when determining the amount to include on line 1a of the Keogh, SEP and SIMPLE Contribuiton Worksheet.
