TurboTax calculates Form 8960, Line 9b using a formula that considers the proportion of state, local, and foreign taxes relative to investment income. Specifically, it applies the ratio of total investment income to adjusted gross income (AGI) and multiplies it by the deductible state, local, and foreign taxes.
Regarding the SALT cap, TurboTax appears to use the actual deductible amount from Schedule A, meaning it does not include amounts exceeding the $10,000 cap.
If you're looking for official documentation within TurboTax, you may need to check Form 8960 Worksheet, which traces the source of the calculation.
Computation of Form 8960 Line B
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
