When you first add optimizable credits and/or deductions, they will be applied in full (even if you don’t benefit from claiming them this year). If you have a linked partner, the credits/deductions will be applied to one of your returns. You can review the initial allocations in the Optimizations table (in the Summary section).1
To optimize your return, complete your return(s), click Check & Optimize, and clear any errors.2 The optimizer then runs thousands of calculations3 to determine whether you should claim a credit, split it, or carry it forward to a future year.
If you change any optimizable inputs (e.g., add another donation receipt), that credit (e.g., donations) will go back to its initial state (e.g., applied in full to one return) until you run the optimizer again.
Note: The optimizer looks for the highest possible combined refund this tax year—it does not support multi-year tax planning (but you can override any results).
If you have a linked partner, generally the credit is applied to the higher-income person’s profile (at the moment the credit is added to the return).
If the optimizer does not run you may need to click Check & Optimize again, and/or clear any errors from your linked partner’s return.
Using—primarily—function minimization, for the math folks out there.