What Is a Sales Tax Audit?

A sales tax audit is an examination by the California Department of Tax and Fee Administration (CDTFA) of your business’s sales and transaction records to verify that you collected, reported, and remitted the correct amount of sales tax.

The CDTFA — which took over from the Board of Equalization in 2017 — audits retailers, wholesalers, contractors, and any business registered (or required to be registered) as a seller in California. If you’ve received an audit notice or are trying to understand what you’re dealing with, here’s how the process actually works.

Who Conducts CDTFA Audits and Under What Authority

The CDTFA’s audit authority comes from California Revenue and Taxation Code § 7054, which gives the department broad power to examine the books, records, and accounts of any person it has reason to believe is required to file a sales or use tax return.

That scope is broader than most business owners expect. “Records” includes not just your sales journals and tax returns, but your general ledger, bank statements, point-of-sale system data, purchase invoices, and exemption and resale certificates. The CDTFA can examine records from up to three years back for a standard audit, and up to eight years when it has evidence of fraud or substantial underpayment.

Auditors are field-trained employees who specialize in specific industries. If your business is in food service, construction, or retail, the auditor assigned to your case likely has significant experience with your industry’s specific exemption issues and common compliance gaps.

What Triggers a CDTFA Audit

The CDTFA uses several selection methods, and unlike the IRS, it is somewhat more transparent about the factors it looks at.

The most common triggers include:

• Industry selection. The CDTFA tracks average tax-to-sales ratios by industry type and compares your reported numbers to your peers. A restaurant or retailer reporting a taxable sales ratio significantly below the industry norm for your category will attract attention.
• Tip or complaint. A competitor, a former employee, or a customer can file a complaint with the CDTFA reporting suspected underreporting. These tips are taken seriously and often generate audits.
• Related audit. If your supplier, contractor, or major customer was audited and your name appeared in their records, the CDTFA may pull your account as part of the same examination.
• Low or fluctuating sales-to-tax ratios. Inconsistent tax reporting — months where your effective tax rate is unusually low relative to gross receipts — is a statistical flag.
• Prior audit history. A previous audit that identified unreported tax or required an adjustment makes future audits more likely.

Types of CDTFA Audits

The type of audit assigned to your account depends largely on the scale of your business and the nature of the issue being examined.

The three formats are:

• Correspondence audit. Conducted entirely by mail. The CDTFA requests specific records or asks you to explain a discrepancy. Typically used for smaller accounts or narrowly defined issues.
• Office audit. You or your representative brings records to a CDTFA field office. More common for small to mid-size businesses where the audit scope is limited to a few key issues.
• Field audit. An auditor comes to your place of business. This is the most common format for larger businesses and is more comprehensive — the auditor has access to your entire operation, your records systems, and can observe your business processes in person. Field audits have the broadest scope and the greatest potential for expansion.

What CDTFA Auditors Look For

The central focus of every CDTFA audit is the reconciliation between your reported taxable sales and what your records actually show.

Auditors typically start with a gross receipts reconciliation: they compare your total sales per tax returns against your bank deposits, point-of-sale reports, and general ledger. If those numbers don’t track, the auditor will work to explain the gap — and any unexplained difference tends to become proposed additional taxable sales.

From there, specific areas of scrutiny include:

• Exemption and resale certificates. Form CDTFA-230 is the California resale certificate. If you accepted resale certificates from customers and sold them product tax-free, the CDTFA will verify that those certificates are valid, on file, and that the buyers actually resold the goods. Invalid or missing certificates mean the sales become taxable.
• Taxable vs. exempt sales classification. Many businesses — particularly in food service, construction, and professional services — have a mix of taxable and exempt transactions. Whether food is hot or cold, whether a service is fabrication or installation, whether a sale was shipped out of state — these distinctions affect taxability and are frequently disputed.
• Sales suppression. The CDTFA looks for patterns consistent with skimming: Z-tape discrepancies, cash register voids at unusual rates, periodic sales that are unusually low, or point-of-sale systems that have been modified.

What the CDTFA Can Assess: Tax, Interest, and Penalties

If the audit results in a deficiency — meaning the CDTFA concludes you underreported taxable sales — you’ll owe the additional tax, plus interest, plus potentially a penalty.

Interest accrues on unpaid tax from the original due date at a rate the CDTFA adjusts annually — currently around 7% per year. This compounds, and for audits covering multiple years, the interest alone can be substantial.

Penalty exposure depends on the facts. A negligence penalty (10% of additional tax) applies when the CDTFA finds that the underpayment resulted from carelessness or failure to keep adequate records. A substantial understatement penalty (10%-25%) applies to larger gaps. Fraud penalties — up to 50% of additional tax — require evidence of intentional evasion, which the CDTFA must affirmatively prove.

What Records to Have Ready

The CDTFA will generally request the following records for each period under audit, and having them organized before the audit begins materially affects how the process goes.

Standard document requests typically include: general ledger and trial balance; sales journals and records; bank statements (all accounts, business and any accounts receiving business deposits); point-of-sale system reports including Z-tapes or daily closeout reports; purchase invoices and purchase journals; resale and exemption certificates for tax-free sales; prior period sales tax returns; and corporate or business tax returns.

The more organized and complete your records, the more controlled the audit tends to be. Gaps in records give the auditor room to use estimation methods — which rarely favor the taxpayer.

Should You Respond to a CDTFA Audit Without Representation

A CDTFA field audit is a legal proceeding, not an accounting exercise — and the statements your accountant or bookkeeper makes to the auditor can be used to expand the audit scope or establish facts that are difficult to walk back.

The short answer is: get representation before the first meeting with the auditor. Not after you’ve already had that meeting. Not after you’ve already handed over documents. The scope of a CDTFA audit can expand significantly based on what the auditor observes or hears in the first few conversations — and a representative who knows what to provide, what to hold back, and how to frame the production of records will have a different result than a business owner who is trying to cooperate their way through it.

Frequently Asked Questions

What is a sales tax audit in California?

A sales tax audit is an examination by the California Department of Tax and Fee Administration (CDTFA) that verifies whether your business collected, reported, and remitted the correct amount of California sales and use tax. The CDTFA reviews your sales records, bank deposits, exemption certificates, and point-of-sale data against your filed returns to identify any discrepancies.

How far back can the CDTFA audit my business?

For standard audits, the CDTFA can go back three years from the later of the due date or the filing date of each return. If the CDTFA has evidence of fraud or a substantial underpayment — generally defined as more than 25% of tax due — the lookback period extends to eight years. There is no statute of limitations when no return was filed.

What triggers a CDTFA sales tax audit?

Common triggers include: a tax-to-sales ratio that falls significantly below the industry average for your business type; a tip or complaint from a competitor, employee, or customer; your name appearing in the records of a supplier or customer who was audited; inconsistent or fluctuating tax reporting over time; and prior audit history with the CDTFA or its predecessor, the Board of Equalization.

Can I handle a CDTFA audit without an attorney or CPA?

Legally, yes — but it’s a significant disadvantage in practice. CDTFA field audits involve complex classification disputes, sampling methodology, and discussions with trained industry auditors. Statements made directly by the business owner can be used to expand the audit scope or establish damaging admissions. Having a representative who knows the audit process manage all CDTFA contact and document production is usually the better approach.

If your business has received a CDTFA audit notice — or you’re concerned about your sales tax exposure — our California sales tax audit defense page covers what to expect and how we approach these cases. Book a free 15-minute call to talk through where you stand.