When creating the T4A slips, you will now notice a checkbox labeled "Exclude Deductions from Gross Commission Income". If checked, the income reported on the agent's T4A will exclude brokerage deductions such as deal fees and splits. This does not affect third-party deductions (such as commission advance loans, garnishments, GST withholdings) or agent expenses.
For additional clarity, consider an agent who made $150,000 in gross commissions. The agent has a 10% split to the brokerage and thus paid $15,000 in brokerage fees. With the "Exclude Deductions from Gross Commission Income" box checked, the T4A will show an income of $135,000. With it unchecked (default behaviour), the T4A will show $150,000.
Additionally, for broker/owners with a 100% "owner deduction" (all of their income is retained by the brokerage), enabling this option means that they will not receive a T4A, as their income net of deductions is zero.