Amounts transferred from your spouse or common-law partner. If your spouse or common-law partner does not need to claim some or all of certain non-refundable tax credits to reduce his or her federal tax to zero, you may be able to transfer those unused amounts to your return.
Things like CPP & EI premiums paid are not transferable in any situation.
Other credits are like the age amount - you can use leftover amounts. Still other credits like medical expenses and donations can be claimed entirely by one spouse or the other.
Here is a link to CRA which will help you!
When doing a coupled return using TurboTax it always looks for the best return possible return for you!