In 2018, the federal government passed new tax legislation for Canadian-controlled private corporations (CCPCs), including incorporated professionals. Effective for taxation years starting in 2019, the small business limit ($500,000 federally and in most provinces) will be reduced by $5 for every $1 of investment income above $50,000. Under the rules, a new definition of adjusted aggregate investment income (AAII) is used to determine the amount of investment income that will grind down the small business deduction, which is effectively eliminated when investment income reaches $150,000 in a given taxation year.  Just as associated corporations must share the small business limit, investment income in associated corporations must be aggregated to determine if the $50,000 threshold has been surpassed and to determine the amount of the small business limit that will be clawed back. The reduced small business limit is then what must be shared within an associated group of companies.