South Dakota Audit Uncovers Vehicle Tax Errors, Triggering Refunds for Overcharged Taxpayers

PIERRE, S.D. — A state audit released in early July has revealed that South Dakota's new online vehicle registration system incorrectly calculated taxes on some transactions, leading to both overpayments and underpayments by vehicle owners. The findings have prompted the state's Department of Revenue to issue refunds and conduct a wider internal review of the system's accuracy.

The audit, which covered the fiscal year from July 2024 through June 2025, focused on the "605Drive" system, which the Department of Revenue implemented in February 2025. Auditors discovered that incorrect trade-in values were sometimes used in tax calculations, which directly impacted the taxable amount for vehicle purchases. The state imposes a 4% excise tax on the purchase price of most vehicles.

According to the audit report, state auditors initially tested a sample of 112 transactions from a total of 750,005 processed during the period. Within that small sample, they identified three transactions with tax overpayments totaling approximately $1,400. This discovery prompted auditors to recommend that the Department of Revenue conduct a more thorough review of its titling and registration processes to identify and refund any other taxpayers who were overcharged.

In response to the audit's findings, the Department of Revenue launched its own internal investigation into the same pool of over 750,000 transactions. The department’s review found that 604 transactions were affected by errors that occurred during a data transfer from the state's previous system to the new 605Drive platform. The department’s deeper analysis uncovered nine additional errors that resulted in about $1,450 in refunds owed to taxpayers. It also found 24 instances where taxpayers had underpaid by a collective $4,200, and 56 other documentation errors that did not have a financial impact.

The Department of Revenue has confirmed that refunds for the identified overpayments have either been processed or are currently in the process of being sent out. However, officials have not yet stated whether the state will seek to collect the $4,200 in underpayments discovered during its review.

This is not the first time the department has faced scrutiny over collection errors. A state audit from the previous year found that the Department of Revenue had collected approximately $530,000 in commercial vehicle fee overcharges, an issue that affected more than 11,000 vehicles registered in South Dakota. The recurrence of systemic errors raises concerns for businesses that operate vehicle fleets, for whom accurate tax and fee collection is a significant operational and financial matter.

For businesses, particularly those in sectors like construction, logistics, and agriculture that rely on multiple vehicles, such errors can create substantial accounting and cash flow challenges. The state’s motor vehicle regulations include penalties for late tax payments, starting with interest of 1% or $5 for the first month and a one-time penalty of 10% of the tax due or $10 after 60 days. While these penalties apply to taxpayer errors, the audit highlights the financial risk when the state's own system is the source of the miscalculation, placing a burden on businesses to verify the government's figures.

For business owners, these kinds of state-level system errors are more than just a headline; they are a practical problem that can quietly drain resources. While the individual amounts in this specific audit may seem minor, they reveal systemic vulnerabilities that can multiply across a fleet of vehicles or over several years. This forces companies to dedicate time and resources to verifying tax assessments that should be correct in the first place. It underscores the reality that businesses cannot blindly trust that automated government systems are calculating their tax liabilities accurately. In our experience, proactive oversight is the only effective defense against being overcharged due to data migration glitches or software miscalculations. This is a core part of the value we provide through our tax preparation and compliance services. We help clients ensure they are not overpaying on state and local taxes, including complex areas like vehicle excise taxes. To ensure your business's tax obligations are managed correctly, contact C&S Finance Group LLC at csfinancegroup.com.

Moving forward, the Department of Revenue will be expected to fully implement the auditors' recommendations for a comprehensive review of the 605Drive system to prevent future inaccuracies. South Dakota businesses and residents who have registered or titled a vehicle since February 2025 should review their transaction records and watch for any further communications from the state regarding potential refunds or corrections.