It depends if you are claiming with your spouse or another person. If you are splitting the interest with your spouse, you will enter the entire amount that is shown on the tax slip in Box 13, and enter the percentage to be claimed on your spouse's return.
If you are splitting these interest amounts with a person other than your spouse, you will only enter the percentage amount in Box 13 that applies to you. You would then issue a copy of the same slip to the other person or persons who are on the account.
Here is more information on the CRA Attribution Rules:
If your T3 or T5 is issued in more than one name, such as your spouse or a child over 18, you can split the amounts.
According to CRA Attribution rules, what you need to do is determine who contributed to the investment and what percentage. You report the interest earned in the same proportion as the funds that were contributed to the account that earned the income. So if these were "your" funds, then you would claim the income on the T3 & T5 slips 100% in your name.
You cannot change the amounts strictly for tax advantages, and you should continue to report it with the same percentages each year, as changing this each year can trigger a review and possible reassessment from CRA. Generally spouse's claim 50/50.
