TurboTax automatically calculates credits and deductions so that you get the best tax benefit. With charitable donations and gifts, this typically results in all donations being claimed on the return of the spouse with the higher net income.
The tax credit on the first $200 of donations and gifts is at a lower rate (15%) than the remaining balance (29%). When you split charitable donations between yourself and your spouse or common-law partner, you effectively cause the tax credit to be 15% of the first $400, reducing the tax credit. Generally, you can claim all or part of your donations, up to the limit of 75% of your net income. For this reason, it is usually better for the person with the higher net income to claim charitable donations on their return, as they can claim a higher amount.
If you’d prefer to override the optimization, here’s how: