If the investment reported on your T5 is a joint investment with your spouse or common-law partner, enter your percentage of the investment in the first box. If the shares are 50% each (50-50) then enter 50% in the firts box, and do not enter a percentage in the second spouse's slip.
For each box that applies to you, enter the full amount from your T5 slip; only your portion is transfered to your return. If you are preparing a coupled return, your spouse's portion is transferred his or her return.
Note: Although this amount does not appear in your spouse's T5 entry window, do not re-enter it there. It has been included on his or her Schedule 4 - Statement of Investment income.
https://turbotax.community.intuit.ca/questions/1189813-where-can-i-find-tax-information-about-capital-gains-and-losses
https://turbotax.community.intuit.ca/questions/1190196-t5-statement-of-investment-income
I have the same issue. This has nothing to do with joint T5 - I am the sole owner of account with investment income but it will not let me get past the Income Slips page unless I check the T5 for my spouse (who has no T5). I visited this page some time after entering in my own T5. This appears like a bug to me.