If you have a negative amount in box 21 of your T5008 slip, it typically relates to futures or options contracts. In this case, you can't use the T5008 section in Wealthsimple Tax. Here's how to report it based on the type of loss:

For a capital loss:

1. Add the Capital Gains (or Losses) section to your profile
2. Enter 0 in the Proceeds column
3. Enter the absolute value of the amount in box 21 in the Cost Base column
   (For example, if box 21 shows -$500, enter 500 as the Cost Base)
4. This will add the capital loss to your Schedule 3

For an investment loss:

1. Add the Carrying Charges and Interest Expenses (Line 22100) section to your profile
2. Enter the absolute value of the amount in box 21 as a carrying charge
   (For example, if box 21 shows -$500, enter 500)
3. This will add the amount to line 22100 and deduct it from your income

For a business loss:

• Report it on your T2125 form for business income

Important notes:

• Always enter the absolute value (positive number) when reporting these losses
• The correct reporting method depends on the nature of your trading activity
• Keep all relevant trading records and documents for your files

If you're unsure about how to classify or report this loss, consider consulting with a tax expert.