Updated October 24, 2026. Quick answer: Line 16 of the California Form 540 is where additions to federal income, taken from Schedule CA (540), go. Line 17 then combines line 15 and line 16 into California adjusted gross income. When a Schedule CA (540) total is negative, the instructions for its line 27 send the amount to the other line as a positive number.
What this line does
The form’s line 16 begins “California adjustments” and then names additions: “Enter the amount from Schedule CA (540), Part I, line 27, column C”. The booklet repeats the source in brackets under the heading.
Line 17 sits just below. Its wording on the form is “California adjusted gross income. Combine line 15 and line 16”. The subtractions that come before it are on California Form 540 line 14.
Who it applies to
The booklet states the condition as “If there are differences between your federal and California deductions, complete Schedule CA (540).” It then says “Follow the instructions for Schedule CA (540).”
Pension and IRA differences are covered on Schedule CA (540) lines 4 and 5, and the Social Security and HSA questions are on whether California taxes Social Security and whether California taxes HSA contributions.
What the instructions say
| Line | What the form says |
|---|---|
| Line 16, the form | “Enter the amount from Schedule CA (540), Part I, line 27, column C” |
| Differences | “If there are differences between your federal and California deductions, complete Schedule CA (540).” |
| What to enter | “Enter on line 16 the amount from Schedule CA (540)” (the part, line and column are those in the form row above) |
| Negative amount | “If a negative amount, see Schedule CA (540)” (the booklet points to the line 27 instructions) |
| Line 17, the form | “California adjusted gross income. Combine line 15 and line 16” |
| Schedule CA, line 27 | “Subtract line 26 from line 10 in column B and column C.” |
| Column B negative | “If column B is a negative number, transfer the amount as a positive number to Form 540, line 16.” |
| Column C negative | “If column C is a negative number, transfer the amount as a positive number to Form 540, line 14.” |
Where the result goes next
Line 16 joins line 15 on line 17. Line 17 then feeds the deduction and taxable income steps that follow on the form. The Schedule CA (540) instruction for Part I line 27 on booklet page 66 also carries each total to Form 540: “Subtract line 26 from line 10 in column B and column C.” For the state overview, see California retirement taxes and whether California taxes pensions.
A worked example
The form prints the arithmetic for line 17: combine line 15 and line 16. This is an illustration, not a state example, using invented amounts.
Suppose line 15 is $50,000 and the Schedule CA (540) column C total on line 16 is $2,000. Line 17 is $50,000 plus $2,000 and that is $52,000 (computed). The amounts are invented for the computation; your own lines come from your own return.
Edition and line numbers
This page reads California 540 Forms and Instructions, 2025 Personal Income Tax Booklet, Franchise Tax Board, and Form 540, California Resident Income Tax Return (2025), Franchise Tax Board, for tax year 2025, the current file the Franchise Tax Board served on 2026-10-24. Check the edition printed on your own form and use that edition’s line numbers.
Common mistakes
- Leaving a negative column C total on line 16. The booklet says “If column C is a negative number, transfer the amount as a positive number to Form 540, line 14.”
- Leaving a negative column B total on line 14. The booklet says “If column B is a negative number, transfer the amount as a positive number to Form 540, line 16.”
- Skipping Schedule CA (540) when your federal and California deductions differ. The booklet says “complete Schedule CA (540).”
Related: California retirement taxes, whether California taxes pensions, Schedule CA (540) lines 4 and 5, whether California taxes Social Security, and whether California taxes HSA contributions.
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- California 540 Forms and Instructions, 2025 Personal Income Tax Booklet, Franchise Tax Board: www.ftb.ca.gov
- Form 540, California Resident Income Tax Return (2025), Franchise Tax Board: www.ftb.ca.gov
- Related official page (not quoted): Franchise Tax Board, 2025 Personal Income Tax Booklet page: www.ftb.ca.gov
Read from the state revenue documents linked above on October 24, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer or the state revenue department is the right place to confirm anything consequential.