Troubleshooting

Box 21 on the T3 for 2024 is just the sum of the amounts in boxes 52 & 53. You need to put whatever is in Box 21 in either 52 or 53 for it to transfer to Schedule 3. It doesn't matter which as they are both taxed at the 50% rate, but for some reason using just Box 53 seems to work better for some people.