@samsonpyng T4A box 48 goes to the T2125, and result of T2125 goes into line 13500 (net business income). Is the amount from T4A box 48 showing up on your T2125?
Check if you have fill out T2125.
T4A box 48 is "Fees for services", which is considered self-employment/business income. This is why the CRA is saying the amount needs to go on line 13500, which is net business income. Line 13500 is calculated based off of the result of the T2125, so if there is no T2125, then line 13500 will be empty.
