Why you need to pay extra attention to T5008 slips?
The software adds the result of [ box 21 - box 20 ] on your T5008 to your capital gain(or loss) on schedule 3.
There is no problem when all your T5008 slips are prepared correctly. However we found a great number of T5008s are misused.
Sometimes the amount in box 20 may not reflect your actual adjusted cost base (ACB). Some T5008 slips are used to record
purchase transactions on which the purchase price is put into box 21 instead of proceeds.
These mistakes would result in totally wrong capital gains (or losses).
Therefore, be very cautious with your T5008s. Don't use it unless you are certain that it is correct.
You may reference your other supporting documents or sources to get correct numbers.