5805: Underpayment of Estimated Tax by Individuals and Fiduciaries (2025)

Who files this form

Form FTB 5805 addresses underpayment of estimated tax by individuals, estates, and trusts for tax year 2025. In most cases, the Franchise Tax Board (FTB) can figure the penalty for you, and you do not need to complete this form.

The form says not to complete or file it if any of these conditions apply:

• Your tax liability after credits, including withholding but excluding estimated tax payments, was less than $500 for either 2024 or 2025, or less than $250 if married/RDP filing separately. This test excludes tax on lump-sum distributions and accumulation distributions of trusts.
• You had no tax liability for 2024, and your 2024 return covered a full 12 months, or would have if you had been required to file.
• Your withholding plus estimated tax payments, paid in the required installments, equals at least 90% of your 2025 tax or 100% of your 2024 tax, and you are not using the annualized income installment method. The prior-year percentage increases to 110% if your 2024 California adjusted gross income (AGI) was more than $150,000, or $75,000 if married/RDP filing separately for 2025.

If your California AGI is at least $1,000,000, or $500,000 if married/RDP filing separately, you must use your 2025 tax rather than your 2024 tax for this comparison unless you meet one of the first two exceptions.

When it's due

For tax year 2025, the short-method penalty calculation uses April 15, 2026 as a payment cutoff. Line 12 treats an underpayment paid before that date differently from one paid on or after that date.

The supplied form does not state a filing deadline for Form FTB 5805.

What you'll need

Have the following information available to complete the applicable parts of the form:

• Your 2025 Form 540, Form 540NR, or Form 541, including tax, credits, and withholding amounts.
• Your 2024 tax return, including the tax shown and California AGI, if using the prior-year tax calculation.
• Records of your estimated tax payments and when the underpayment was paid.
• Actual withholding amounts and dates if you report withholding that was not taken in equal installments.
• Income and deduction amounts for each applicable period if using the annualized income installment method.
• An explanation if requesting a penalty waiver. Attach a statement if you need more space.

Enter your name as shown on your return and your SSN, ITIN, or FEIN.

How to file

Attach Form FTB 5805 to the back of your Form 540, Form 540NR, or Form 541. Check the underpayment of estimated tax box on the applicable return:

• Form 540, line 113.
• Form 540NR, line 123.
• Form 541, line 45.

All Form FTB 5805 filers must complete Parts I and II. If you use the short method, enter the penalty from line 13 on the applicable return line listed above and check the “FTB 5805” box.

The supplied form does not provide a mailing address or e-filing instructions.

Common mistakes

• Including estimated payments with withholding. Part II, line 3 must not include estimated tax payments.
• Using the short method without checking eligibility. The form directs you to the instructions to determine whether you can use it. If you answered “Yes” to Part I, Question 2, skip the short method and go to Part III.
• Using Part III for steady income. Use the annualized income schedule only if you earned taxable income at an uneven rate during 2025, not at approximately the same rate each month.
• Skipping the preliminary calculation. Complete Part II, lines 1 through 6 before completing Part III.
• Mixing methods across payment dates. If you use the annualized income installment method for one payment due date, you must use it for all payment due dates.
• Reporting uneven withholding totals that do not match your return. The four amounts in Part I, Question 3 must equal the withholding reported on the return lines identified there.
• Using the wrong periods for an estate or trust. Part III provides separate period-ending dates for estates and trusts. Fiscal-year filers must adjust dates accordingly.

Questions people ask

Can the FTB calculate the penalty for me?

Yes. The form says that in most cases, the FTB can figure the penalty and you do not need to complete Form FTB 5805.

How do I request a penalty waiver on this form?

Answer “Yes” to Part I, Question 1 and provide an explanation. Attach a statement if you need more space. Also check the underpayment box on Form 540, line 113; Form 540NR, line 123; or Form 541, line 45.

Could the annualized income installment method help if my income varied during the year?

Yes. The form says this method may benefit people who earned taxable income unevenly during 2025. It may produce a smaller required installment than the regular installment method.

What if my short-method total underpayment is zero or less?

If Part II, line 10 is zero or less, stop. The form says you do not owe the penalty and should not file Form FTB 5805.

Official sources

• https://www.ftb.ca.gov/forms/2025/2025-5805.pdf