The Franchise Tax Board issues notices when information reported on California tax returns does not reconcile with third-party data, bank records, or supporting documentation. In the 2026 filing season for tax year 2025 returns, common bookkeeping errors continued to generate the majority of automated FTB notices and follow-up correspondence. This publication reflects tax law and regulations applicable as of May 2026 and is subject to change without notice.
This article examines the most frequently observed bookkeeping errors that lead to California FTB notices in 2026, the specific filing or reporting mismatches they create, documentation patterns associated with increased scrutiny, and official FTB resources for general reference.
Most Common Bookkeeping Errors Triggering FTB Notices
| Bookkeeping Error | Typical Cause in Records | Resulting FTB Notice or Adjustment |
|---|---|---|
| Failure to record California conformity adjustments | OBBBA deductions taken on federal return but not adjusted on Form 540 | Proposed add-back of non-conforming deductions |
| Unreconciled bank and credit card accounts | Bank deposits or credit card charges not fully classified | Underreported or overstated income/expenses |
| Incorrect 1099-NEC/1099-MISC reporting | Independent contractor payments not tracked or reported | Mismatched third-party information |
| Improper Form 593 real estate withholding | Withholding calculations or exemptions not properly documented | Withholding discrepancies and seller refund delays |
| Payroll withholding and deposit errors | California withholding not reconciled to Form 592/593 filings | Wage and withholding mismatches |
How Bookkeeping Errors Lead to FTB Notices
Discrepancies between the taxpayer's books and the filed California return trigger the FTB's automated underreporter and matching programs. When bank deposits exceed reported income or when deductions claimed on the federal return are not properly adjusted for California conformity rules, the system generates a notice requesting explanation or additional documentation. The Franchise Tax Board also reviews PTE elective tax elections, June 15 payments under SB 132, and real estate transactions for proper Form 593 (accessed May 25, 2026) handling.
California requires taxpayers to maintain books and records sufficient to substantiate all items on the return for at least four years from the later of the due date or filing date of the return. Failure to respond to an FTB notice within the time frame stated on the notice may result in the proposed adjustments becoming final assessments.
Compliance Resources and Tools
Official FTB forms and instructions, including Publication 4058 and Form 540 instructions (both accessed May 25, 2026), are available on the Franchise Tax Board website.
- Common bookkeeping errors, particularly failure to make California conformity adjustments for OBBBA provisions, frequently generate FTB notices.
- Unreconciled bank accounts and incomplete third-party reporting (1099s and Form 593) are among the most common triggers observed in 2026.
- Proper classification of income, expenses, and withholding items helps maintain consistency between books and filed returns.
- The FTB cross-references returns against third-party data from banks, employers, and escrow agents.
- Retention of complete, contemporaneous records for at least four years supports timely response to any notices received.
- Official FTB publications provide general guidance on recordkeeping and common filing adjustments.
References
- Franchise Tax Board. (2026). Publication 4058: Collection and Enforcement. FTB.ca.gov. Accessed May 25, 2026. https://www.ftb.ca.gov/forms/2026/2026-4058.pdf.
- Franchise Tax Board. (2026). Instructions for Form 540. FTB.ca.gov. Accessed May 25, 2026. https://www.ftb.ca.gov/forms/2026/2026-540-instructions.pdf.
- Franchise Tax Board. (2026). Form 593 – Real Estate Withholding Statement. FTB.ca.gov. Accessed May 25, 2026. https://www.ftb.ca.gov/forms/2026/2026-593.pdf.
- Franchise Tax Board. (2026). Understanding FTB Notices. FTB.ca.gov. Accessed May 25, 2026. https://www.ftb.ca.gov/about-ftb/notices/index.html.
- Franchise Tax Board. (2026). Recordkeeping Requirements for California Taxpayers. FTB.ca.gov. Accessed May 25, 2026. https://www.ftb.ca.gov/file/business/recordkeeping/index.html.
- Franchise Tax Board. (2026). Pass-Through Entity Elective Tax – Form 3804. FTB.ca.gov. Accessed May 25, 2026. https://www.ftb.ca.gov/forms/2026/2026-3804.pdf.
The information contained in this publication is provided for educational and general informational purposes only. It does not constitute tax advice, accounting advice, legal advice, or any other form of professional advice and does not create a client-professional relationship.
The content reflects tax law and regulations applicable on the date of publication only and is subject to change without notice. Examples and illustrations are hypothetical and do not represent any specific taxpayer situation.
No reader should act or refrain from acting on the basis of this publication without first obtaining specific written advice from a licensed CPA based on the reader's individual facts and circumstances.
Any federal tax advice contained herein is not intended or written to be used, and cannot be used, for the purpose of avoiding penalties that may be imposed under the Internal Revenue Code.
Parsi Team Specific Notice: This publication was prepared by non-licensed content personnel under the direct supervision and final approval of a licensed CPA. The reviewing CPA assumes professional responsibility for the technical accuracy and compliance of the content.