A Texas sales tax audit is a line-by-line review by the Texas Comptroller of Public Accounts covering up to four years of your transactions, with penalties reaching 20 percent of any tax owed plus interest at the prime rate plus one percent. The auditor reconciles what you reported on your sales tax returns against your general ledger, federal income tax filings, and bank deposits, and then scrutinizes every exemption and deduction you claimed. The burden of proof sits with you: any transaction you cannot document as nontaxable gets treated as taxable.1Legal Information Institute. 34 Texas Admin Code 3.339 – Statute of Limitations
The Notification Letter and the Four-Year Window
The process opens with a formal audit notification letter, usually sent by certified mail. The letter names the auditor assigned to your case, the tax types under review, and the exact reporting periods. The Comptroller’s lookback window extends four years from the date the tax became due and payable, which is why most audits reach back roughly four years from the notification date.1Legal Information Institute. 34 Texas Admin Code 3.339 – Statute of Limitations
Three exceptions remove that window entirely. The statute of limitations does not apply if you filed a fraudulent return intending to evade tax, if you failed to file a return at all, or if your return contained a “gross error” — defined as an understatement of at least 25 percent of the tax actually due.1Legal Information Institute. 34 Texas Admin Code 3.339 – Statute of Limitations When any of these apply, the Comptroller can assess tax, penalties, and interest with no time limit.
Check the oldest period on your notification letter. If it is approaching the four-year mark, the auditor may ask you to sign a waiver extending the statute of limitations. You are not required to sign. Refusing may push the auditor to issue a quick assessment based on whatever information is already on hand, so weigh the trade-off before responding.
Your First Moves After the Letter Arrives
The notification requests an entrance conference, a getting-to-know-your-business meeting. The auditor will ask about your corporate structure, your accounting software, how you process sales, and what point-of-sale systems you use. Before that meeting, designate a single point of contact to handle every communication with the auditor. That contact can be you, a CPA, or an attorney. Multiple people answering requests produces conflicting answers and signals disorganization.
You have the right to hire professional representation before fieldwork begins. Securing a representative also gives you a legitimate reason to ask for additional time ahead of the entrance conference. Use that time to organize records, review your past filings, and identify areas where your documentation is weak.
Requesting a Managed Audit
Many business owners never learn they can conduct the audit themselves. Texas Tax Code Section 151.0231 establishes a managed audit program where you review your own invoices, checks, and accounting records under the Comptroller’s oversight instead of handing everything to a state auditor.2Texas Comptroller of Public Accounts. Managed Audit Policy and Procedures – Auditing Fundamentals The incentive is real: unless the managed audit uncovers fraud or willful evasion, the Comptroller cannot assess a penalty and may waive all or part of the interest. Those waivers do not cover tax you collected from customers but failed to remit.
To qualify, submit your request to the field audit manager within 60 days of the date on your audit notification letter. The Comptroller will not approve a managed audit if fieldwork has already started or if a prior audit of your business took 80 hours or less, a signal that your records are simple enough for a standard review. Other factors include your understanding of taxability rules, your compliance history, and whether your records are actually available for the periods in question.2Texas Comptroller of Public Accounts. Managed Audit Policy and Procedures – Auditing Fundamentals
If approved, you have 45 days to submit a signed managed audit agreement, an audit plan describing your procedures, a timeline for completion, and original data files containing your sales or purchase information. Miss that window and a second letter gives you a 10-day extension. Miss that too and the request is denied, dropping you back into a standard audit. A managed audit also entitles you to a refund if the review uncovers overpaid tax, which a traditional audit rarely produces voluntarily.
Records the Auditor Will Demand
Texas law requires you to keep every record needed to verify your sales tax liability for at least four years from the date the record was created.3Texas Public Law. Texas Tax Code Section 151.025 – Records Required to Be Kept If you store records electronically, your system must let the auditor extract data in a standard, usable format. Expect to produce your general ledger, sales journals, bank statements, federal income tax returns, and your filed Texas Sales and Use Tax Returns (Form 01-114).4Texas Comptroller of Public Accounts. Texas Sales and Use Tax Forms
The auditor’s first job is reconciliation. They compare the gross sales you reported to the Comptroller against what you reported to the IRS and what your bank deposits show. Gaps draw the most scrutiny. If your federal return shows $2 million in revenue but your sales tax returns report $1.5 million in gross sales, the auditor will want to know where every dollar of that difference went, and you will need documentation proving each excluded amount was legitimately nontaxable.
Resale and Exemption Certificates
Nontaxable transactions are the single biggest area of audit exposure. You carry the burden of proving a sale was exempt, not the other way around. Texas uses one form for both purposes, Form 01-339. The front is the Texas Sales and Use Tax Resale Certificate; the back is the Texas Sales and Use Tax Exemption Certification.5Texas Comptroller of Public Accounts. Texas Sales and Use Tax Exemption Certification
For sales-for-resale, the certificate must include the purchaser’s name, address, Texas sales tax permit number (11 digits), a description of the items purchased, and the purchaser’s signature and date.6Texas Comptroller of Public Accounts. Texas Sales and Use Tax Frequently Asked Questions You must keep these certificates in your records for four years. A certificate is invalid if it is incomplete, unsigned, or contains information you reasonably knew was false at the time of the sale. Giving a false resale certificate is a criminal offense ranging from a Class C misdemeanor to a second-degree felony depending on the amount of tax evaded.5Texas Comptroller of Public Accounts. Texas Sales and Use Tax Exemption Certification
For exemption certificates, the purchaser must state the specific legal basis for the exemption. Manufacturing exemptions must reference the applicable provision under Texas Tax Code Section 151.318, which covers items like component parts of products manufactured for sale and equipment directly used in manufacturing.7Legal Information Institute. 34 Texas Administrative Code 3.300 – Manufacturing, Custom Manufacturing, Fabricating, Processing The certificate must link the purchase to the exempt use. A vague statement that the buyer “is a manufacturer” will not satisfy the auditor.
How Sampling Works and How to Challenge It
Fieldwork can happen on-site at your business or remotely through secure transfer of electronic files. For most businesses, the auditor samples transactions rather than reviewing every one. The Comptroller has statutory authority under Section 111.0042 of the Tax Code to use sampling when your records are too voluminous for a complete review, when records are inadequate, or when a full review would cost more than it is worth relative to the expected result.8Texas Comptroller of Public Accounts. Audit Sampling Manual The auditor picks a sample period, often a few months out of the four-year window, calculates an error rate from a detailed transaction review, and projects that rate across the entire audit period.
Before using any sampling technique, the Comptroller must notify you in writing of the procedure.8Texas Comptroller of Public Accounts. Audit Sampling Manual You have two statutory paths to challenge a sample. If you can demonstrate that a specific transaction in the sample period is not representative of your normal operations, that transaction gets pulled from the sample and assessed separately. If you can show the sampling method itself does not follow generally recognized sampling techniques, the projected portion of the audit gets thrown out entirely and the Comptroller must start that portion over.
Seasonal businesses should pay attention to which months the auditor selects. If the sample covers your peak holiday season but your off-season has a different sales mix, the projected error rate will be skewed. Monthly revenue breakdowns and product mix reports can support an alternative sample period.
When your records are missing or inadequate, the auditor shifts to indirect methods. The most common is the markup method, which calculates taxable sales from your cost of goods sold and an assumed industry markup percentage. These estimates almost always produce a higher liability than a review based on actual records. Poor recordkeeping costs real money as a mathematical certainty, not a theoretical risk.
Respond promptly to every written information request. Delays push the auditor toward assumptions and estimates that favor the state. Keep a log of every document you provide and every request you receive.
Penalties and Interest
When an audit produces a deficiency, the Comptroller adds both penalties and interest to the unpaid tax. The penalty depends on how late the tax is:
- 1 to 30 days past due: 5 percent of the tax owed
- More than 30 days past due: 10 percent of the tax owed
- After the Notice of Tax Due date: an additional 10 percent, bringing the total penalty to 20 percent
A $50 late-filing penalty applies for each reporting period where a return was filed late, even if no tax was due.9Texas Comptroller of Public Accounts. Penalties for Past Due Taxes
Interest accrues on unpaid tax at the prime rate plus one percent. That variable rate is set annually and runs from the original due date of the tax, not the date the audit concludes. On a four-year audit, interest alone can add 20 to 30 percent to the underlying tax liability depending on the rate environment. If you elected a managed audit, the Comptroller may waive penalties entirely and reduce or eliminate interest.2Texas Comptroller of Public Accounts. Managed Audit Policy and Procedures – Auditing Fundamentals
The Exit Conference
After fieldwork, the auditor prepares an Audit Report Summary with the proposed additional tax, applicable penalties, and accrued interest. You receive this report at the exit conference. This is your last chance for informal resolution before the assessment becomes official.
Treat the exit conference as a negotiation. Your representative can challenge specific line items, present additional exemption certificates, or argue that the sampling methodology produced distorted results. Any reduction in the proposed liability needs to happen here. Once the Comptroller issues a formal Notice of Determination, the process shifts to the administrative appeals track with far more procedural requirements.
Contesting the Assessment
If you disagree with the findings after the exit conference, the formal dispute begins when the Comptroller issues a Notice of Determination. You have exactly 60 days from the date of that notice to file a written request for a redetermination hearing.10State of Texas. Texas Tax Code Section 111.009 – Redetermination Miss this deadline and the determination becomes final. There is no late-filing exception. The request must include a Statement of Grounds explaining specifically what errors you are contesting and why.
You submit the request and Statement of Grounds to the Comptroller’s Audit Processing Section by mail, email, or fax.11Legal Information Institute. 34 Texas Admin Code 1.10 – Requesting a Hearing After filing, the Comptroller may ask you to produce documentary evidence supporting your position. If that request includes resale or exemption certificates, you typically have 90 days to submit them. Certificates not submitted within that window cannot be used as evidence later in the process. This hard cutoff catches many taxpayers off guard.
Administrative Hearings and Judicial Review
Your case first goes to the Comptroller’s Administrative Hearings Section, where staff try to resolve the dispute by agreement with the auditor. Roughly two-thirds of all hearing requests are settled at this stage without ever reaching a formal hearing.12Texas Comptroller of Public Accounts. Giving Taxpayers Easier Access to Court If no agreement is reached, the case is docketed at the State Office of Administrative Hearings (SOAH), where an Administrative Law Judge conducts a formal hearing.
At the SOAH hearing, both sides present evidence, call witnesses, and submit legal arguments. The proceeding focuses on whether the Texas Tax Code was correctly applied to your specific transactions. You might argue that transactions classified as taxable sales were actually nontaxable sales for resale, supported by valid certificates that were not available during fieldwork. The ALJ issues a Proposal for Decision that goes back to the Comptroller, who makes the final administrative determination.
If that decision goes against you, judicial review is available. Texas law provides two paths. If you completed the SOAH process, you can proceed to district court without first paying the disputed tax. Alternatively, you can bypass the administrative hearings process entirely by paying the disputed tax under protest and filing suit directly.12Texas Comptroller of Public Accounts. Giving Taxpayers Easier Access to Court Either path requires an attorney experienced in Texas tax litigation and adds significant time and expense.
Voluntary Disclosure Before the Audit Starts
If you already know your business has unreported or underreported sales tax liability and the Comptroller has not yet contacted you, the Voluntary Disclosure Agreement program is a far better outcome than waiting to be audited. The program waives all statutory penalties and, in most cases, waives interest as well. The Comptroller limits its review to reports due within four years of the date you first make contact.13Texas Comptroller of Public Accounts. Voluntary Disclosure Program
To qualify, your business must meet three conditions: the Comptroller has not previously contacted you about the liability, verbally or in writing; you have not received a notification of an audit or examination; and the tax type is one the Comptroller administers (all qualify except taxes collected under the International Fuel Tax Agreement).
One limit matters: penalty and interest waivers do not apply to tax you collected from customers but failed to remit to the state. The Comptroller treats collected-but-not-remitted tax as trust fund money, and there is no lookback limit on those amounts.13Texas Comptroller of Public Accounts. Voluntary Disclosure Program The difference between a voluntary disclosure and a standard audit on a four-year liability can easily reach tens of thousands of dollars in waived penalties and interest.