Useful estimates without pretending every fee is exact.
Our goal is to get a buyer close enough to budget a deal and notice meaningful differences in a dealer quote. We deliberately label transaction-specific figures as estimates.
What the headline OTD number means
We define OTD purchase price as the negotiated vehicle price plus modeled transaction tax, dealer/doc fee, title, registration and any extra fees entered by the user. Trade-in value and rebates are then shown separately as credits toward the estimated amount due.
How state tax is modeled
Each jurisdiction has a baseline vehicle-purchase tax type and rate. Special systems keep their local names, such as Georgia TAVT, North Carolina Highway Use Tax and South Carolina’s Infrastructure Maintenance Fee, rather than being mislabeled as ordinary sales tax.
Trade-in treatment
State rules can allow a full taxable-value reduction, no reduction, a capped reduction or purchase-type restrictions. The calculator applies the baseline rule and flags states where eligibility or minimum-value rules make the result more approximate.
Local taxes
Where local vehicle tax may apply, V1 lets the user add the local percentage manually. We do not silently invent a ZIP-based rate. This is a deliberate accuracy choice until a reliable local-rate source is integrated.
Registration, title and dealer fees
Title can be relatively stable, while registration may depend on vehicle value, age, weight, fuel type, county, municipality or plate status. Dealer documentation fees may also vary by dealership. We use practical planning defaults and keep dealer-controlled amounts editable.
Rebates
Manufacturer rebates and dealer discounts can receive different tax treatment. In the baseline engine, a rebate reduces the estimated amount due but does not automatically reduce taxable value. This is intentionally conservative.
Source policy
We prioritize official state revenue, DMV, transportation and motor vehicle agencies. Each state calculator links to the government sources used for review so buyers can verify rules that matter to their transaction.
Update process
State rules are stored in version-controlled TypeScript/structured data, not editable CMS rich text. Editorial guides and explanations can live in Payload. This keeps calculation changes reviewable and testable.