They would need to claim it according to how much each of them contributed to it. If both of them contribute 50/50, then you will specify in the software that one parent's share is 50% and that it is a joint account. Enter the amount from the slip only on one tax return. Then you do the same with the other person's tax return, specify that it is a joint tax return and her percentage.
Amount to report = personal amount contributed / total amount contributed
For example;
Amanda and Phillip opened an investment account together that pays off interests. Amanda contributed $1,000 and Phillip contributed $3,000.
They received a T5 slip with both names on it and an amount of $100 in Box 13.
Each will have to report a portion of this income in their tax returns:
Amanda will report: $00 x $1,000/$4,000 = $25
Phillip will report : $100 x $3,000/$4,000 = $75
To split the amount in TurboTax Online, enter the T5 slip for one spouse, then enter the percentage of slip to claim on the other spouse's tax return. If you are preparing your parent's returns together, then TurboTax will automatically split the amount.
For more information please refer to the following TurboTax article: