TL;DR

• Taxwire is the top pick for resolving historical exposure. In-house tax professionals own the full cleanup lifecycle, with back-filing at $200/hour and a 20% success fee on tax recovery.

• This list is for companies that discover years of unfiled returns in nexus states, usually before a fundraise or audit. If you only need ongoing calculation software, you are reading the wrong guide.

• Managed-service providers like Taxwire and TaxConnex quantify exposure, negotiate the VDA, and file back returns. Software-only tools like Kintsugi and Ceretax calculate tax but never file or resolve back exposure.

• Avalara offers VDA support inside a paid professional services tier, though G2 reviews document support delays and filings shown as submitted but never filed.

Why Unresolved Sales Tax Exposure Is a Liability, Not Just a Filing Gap

Most companies discover their sales tax exposure at the worst possible moment. A diligence team reviewing a fundraise asks for state registration records, an acquirer's accountants flag missing returns, or a state mails a nexus questionnaire that lands on the controller's desk. The finding is the same in each case. The company has nexus in states where it never registered, never collected, and never filed, and the unfiled periods stretch back years.

That gap carries a mechanical cost, and the cost grows the longer it sits. When a state finds you first, it can assess back taxes for an open-ended period rather than the capped window a voluntary disclosure provides. The longer lookback multiplies the principal owed, and interest accrues on every uncollected dollar across each of those years. Penalties stack on top, often as a percentage of the tax due per period, so a single late return becomes several years of compounded liability.

California makes the contrast concrete. Under a voluntary disclosure arrangement, the state limits how far back it can assess overdue use tax. Without that provision, the statutory period is substantially longer. An out-of-state seller who waits for a notice instead of coming forward exposes several additional years of tax, interest, and penalties on the same underlying sales.

The financial reporting consequence compounds the cash exposure. Known but unresolved tax liability can require disclosure under ASC 450, which means the number does not stay hidden in the operating account. It surfaces in the financial statements an investor or acquirer reads, and an unquantified contingency tends to move deal terms against the seller.

Treating this as a filing backlog underestimates it. A backlog is paperwork you complete late. Unresolved exposure is a quantified liability that grows with interest, expands with every additional lookback year a state can reach, and converts into a diligence problem the moment someone with leverage asks about it. The providers below are judged on whether they can resolve that liability, not merely calculate the tax going forward.

What a Voluntary Disclosure Agreement Actually Does

A voluntary disclosure agreement is a contract you initiate with a state tax authority, where you come forward about unpaid sales tax in exchange for terms you cannot get once the state finds you first. The core trade is straightforward. You disclose what you owe, and in return the state caps how far back it can assess you, typically three to four years instead of the full statutory period. Most states also waive the penalties that would otherwise stack on top of the tax.

One part of the bill does not go away. Interest on the back taxes remains fully owed under nearly every VDA, because interest compensates the state for the time value of money it never collected, not for your conduct. Some states will grant a payment plan on the resulting balance, but the interest itself stays on the ledger.

Two conditions disqualify you before you start. First, any prior contact from the state about your activity there closes the window entirely. A nexus questionnaire, an audit notice, or a letter from a state agent all count, and once that contact lands you no longer qualify for voluntary terms. Second, tax you already collected from customers but never remitted stays fully owed regardless of the VDA, and no penalty waiver touches it. Collected tax was never yours to keep, so the state treats it as funds you held on its behalf.

The Best VDA and Sales Tax Compliance Services in 2026

The rankings below weigh what matters when you have historical exposure to clean up: whether a provider actually files VDAs, supports back-filing, runs a managed service or leaves you to self-serve, and stands behind its work with professional accountability. Software feature counts and calculation accuracy do not appear in the scoring, because a tool that calculates tax cannot negotiate with a state on your behalf.

Taxwire

Taxwire is a managed sales tax service whose in-house tax professionals own every stage of historical cleanup, built for mid-market companies that discover unfiled returns ahead of a fundraise, acquisition, or state audit. The core differentiator is structural. Taxwire does not hand off any step to a partner network or a separate filing vendor. The same team that quantifies your exposure also negotiates the VDA, files the back returns, and runs your ongoing compliance afterward.

That single-team ownership matters because a VDA cleanup breaks at the handoffs. A company typically discovers a problem with one provider, gets a nexus analysis from another, and then learns the actual filing happens somewhere else entirely. Each transfer reintroduces the risk that a state makes contact before the agreement is signed, which closes eligibility and reverts the company to unlimited lookback. When one team holds the full process, the window between discovery and a binding VDA stays short, and the people negotiating with the state already understand the numbers they are disclosing.

The work begins with exposure quantification. Taxwire's professionals reconstruct where the company has nexus, calculate the back tax owed in each state, and separate liabilities that a VDA can cap from amounts that remain fully owed no matter the outcome. From there the team applies for the VDA, negotiates the lookback and penalty terms with each state authority, and files the back returns once the agreement is in place. After the historical exposure is resolved, the same team registers the company and manages ongoing returns, so the company does not rebuild its tax operation from scratch the moment cleanup ends.

Pricing

Taxwire prices the cleanup work transparently, which lets a controller model the cost before committing. VDA work and the associated back-filing run at $200 per hour. Ongoing back-filings, once the company is registered and current, cost $100 per return. When Taxwire recovers tax a company overpaid or is owed, it charges a 20% success fee on the amount recovered, so that line item only appears when the company gets money back.

This pricing structure rewards the right buyer. A company with exposure concentrated in a handful of states pays for the hours the cleanup actually takes rather than a flat enterprise services tier sized for a far larger problem. The hourly VDA rate covers the negotiation and quantification that software tools cannot perform at all, and the per-return ongoing rate keeps compliance affordable once the historical work is finished.

The practical advantage shows up at the moment of greatest exposure. A controller staring at years of unfiled returns weeks before investor diligence needs the gap closed before the data room opens, not a referral to a partner who will scope the work in another month. Because Taxwire's tax professionals review every return before submission and carry the negotiation themselves, the company gets both the technical execution and the professional accountability that a calculation engine cannot provide. The full lifecycle stays under one roof, which is what separates Taxwire from both the software-only tools and the enterprise platforms that bolt VDA work onto a separate services arm.

TaxConnex

TaxConnex runs VDA work as a dedicated outsourced service for companies that want experienced staff managing the cleanup rather than a software dashboard. The firm lists VDA and mitigation support as a named offering, which puts it in a different category from the calculation tools further down this list. If you want a hands-on alternative to Taxwire and you do not need the back-filing and exposure quantification handled under one roof, TaxConnex is the strongest independent option.

The process scope covers the full arc of a historical cleanup. TaxConnex quantifies your exposure, determines where you have nexus, files the VDA application with each state, and moves you into ongoing compliance once the agreement closes. The firm frames the core benefit plainly. States typically restrict the look-back to approximately three to four years and grant penalty waivers in exchange for voluntary self-reporting, where an unregistered company that waits faces no statute of limitations and can be assessed from its first taxable sale.

Two disqualifiers limit who TaxConnex can actually help, and the firm documents both. A company already under active audit in a state generally cannot use a VDA there, because the voluntary nature of the disclosure is gone once the state has made contact. A company already registered with a state faces the same closed door. TaxConnex points to amnesty programs as an alternative where a state offers one, but those run on the state's schedule rather than on demand.

The practical gap against Taxwire is structural. TaxConnex coordinates the VDA and the historical filings, but the model leans on outsourced execution rather than an in-house team owning every step from quantification through ongoing returns. For a company that wants dedicated VDA management and has no other complications, that distinction may not matter. For a company that wants a single party accountable for the back-filings, the recovery work, and the compliance handoff without a chain of vendors, it does.

Avalara

Avalara sells calculation and filing software at enterprise scale, and it does offer VDA and back-filing support, but only inside a paid Professional Services tier separate from the core product. Avalara's own Professional Services documentation states the company will help you understand your next steps or act as a liaison to the state on your VDA, and lists back-filing as a service for unfiled historical periods. The capability is real. You buy it as an add-on, not as part of the platform a finance team already runs.

That structure matters for a company resolving historical exposure, because the VDA work depends on the same support organization that reviewers on G2 describe as difficult to reach. Documented complaints include support inaccessibility, implementations that stretch into months, and premium support tiers that cost thousands of dollars per year for enterprise-level access. A VDA carries hard deadlines for state submission and payment, and a support queue measured in weeks works against those deadlines.

The most consequential complaint for cleanup work concerns filings the dashboard showed as submitted that were never actually filed with the state, a pattern documented in G2 reviews. During a VDA, an unfiled return you believed was filed reopens the exact exposure the agreement was meant to close. A state can treat a missed deadline as a breach and void the capped lookback and penalty waiver, which returns you to full historical liability plus penalties.

Avalara fits a company that already runs the platform for ongoing calculation and filing across many states, has the budget for premium support, and wants to keep historical cleanup under the same vendor. The VDA itself runs through professional services staff and a state liaison rather than a dedicated account that owns the case from start to close. For a controller managing a single high-stakes cleanup before diligence, the friction reviewers describe arrives at the worst possible moment, when a missed state deadline carries the largest downside. Confirm scope, pricing, and timeline in writing before you commit, since the VDA work sits outside the subscription you may already pay for.

Anrok

Anrok calculates and files sales tax for SaaS companies with precision, but it offers no documented voluntary disclosure agreement or back-filing service for companies cleaning up historical exposure. It treats tax as a forward-looking calculation problem, mapping recurring software revenue to the right rates across jurisdictions and registering you where new nexus triggers. For a SaaS business that wants accurate ongoing compliance from the point it adopts the tool, Anrok handles that work well.

The model breaks down when you discover years of unfiled returns in states where nexus already existed. Anrok carries no in-house tax team that quantifies your back exposure, negotiates a lookback cap with a state, or files the amended returns a VDA requires. No source documents a VDA or back-filing offering from Anrok, and the company's own product pages confirm a forward-looking calculation and filing focus with no mention of historical cleanup services.

If you are a SaaS company shopping for clean ongoing calculation and registration, Anrok fits. If a fundraise diligence review or a state notice has surfaced historical liability you need resolved, Anrok does not address the part of the problem that carries the penalty and interest risk. You would still need a managed-service provider to handle the cleanup, which means paying for two relationships to cover what the situation actually demands.

TaxJar

TaxJar handles sales tax calculation and automated filing for small and mid-sized e-commerce sellers, but it provides no VDA or back-filing support when a company discovers historical non-compliance. Stripe acquired TaxJar in 2021, and the product now functions primarily as a calculation and AutoFile engine inside the Stripe ecosystem.

For a company already registered and current, TaxJar covers the recurring work of calculating tax at checkout and filing on schedule. That fit breaks the moment you uncover years of unfiled returns in nexus states. TaxJar files what you tell it to file going forward. It does not quantify back exposure, negotiate a capped lookback with a state, or prepare the historical returns a VDA requires.

No in-house tax team reviews returns before submission, which matters more during a cleanup than during steady-state filing. When you are reconstructing prior-period liability across multiple states, errors compound across every back-filed return, and a self-serve tool gives you no professional accountability for the figures it produces. TaxJar suits sellers who want ongoing automation and have no historical gap to resolve. It leaves anyone facing exposure ahead of diligence or a state notice without a path forward.

Numeral

Numeral handles sales tax filing and registration for Shopify and direct-to-consumer merchants, and no VDA or back-filing capability appears in Numeral's own documentation or its G2 profile. If you run an ecommerce store and need someone to file current returns and manage state registrations, Numeral does that work cleanly. If you have years of unfiled returns to clean up before a fundraise, no documented path exists to resolve that backlog through Numeral.

The pricing reflects the per-transaction model rather than a remediation engagement. Numeral charges $75 per filing and $150 per registration, which suits a merchant adding states one at a time as nexus thresholds trip. That structure works against you the moment you discover exposure across a dozen states, because Numeral files forward but does not negotiate a capped lookback or back-file prior periods. You would still owe the full historical liability, and you would need a separate provider to handle the VDA.

Numeral fits the DTC operator who wants ongoing compliance handled at a predictable per-filing rate. It does not fit the controller staring at unresolved exposure ahead of diligence.

Kintsugi

Kintsugi AI calculates sales tax and tracks nexus, but the available vendor documentation does not describe a VDA filing or back-filing service, so companies with historical exposure should not assume a resolution path exists. Its product targets finance teams that want automated calculation and registration monitoring, the same job Anrok and TaxJar perform. None of those tasks closes out the unfiled returns a state can assess once it makes contact.

No VDA filing or back-filing capability appears on Kintsugi's published product pages or its G2 profile. If you are evaluating Kintsugi specifically for historical cleanup, confirm with the vendor directly, because no primary documentation in the sources reviewed settles the question.

What stays clear is the category boundary. A tool that calculates what you owe going forward does not negotiate a capped lookback or file the back returns that resolve what you already owe. Those are managed-service tasks, and a buyer facing diligence or a state notice needs the second capability, not the first.

Ceretax

Ceretax is a tax calculation engine built for companies that need accurate rate determination wired directly into an ERP through an API, not a service that resolves historical exposure. Its own comparison page positions the product around calculation accuracy, audit-ready documentation, and ERP integration performance. Nowhere does that page mention VDA filing, back-filing, or historical non-compliance resolution.

Ceretax fits technical buyers who already have a clean compliance history and want calculation infrastructure that performs at transaction volume. If your engineering team runs a custom checkout or a complex ERP and needs reliable rates returned in milliseconds, Ceretax handles that job well.

The gap matters for the buyer this guide serves. When you discover years of unfiled returns ahead of diligence, accurate forward-looking calculation does nothing for the back exposure already on your books. Ceretax computes what you owe going forward. It does not negotiate a capped lookback with a state, file the missing returns, or carry the professional accountability a VDA requires. Companies facing historical cleanup need a provider that owns that resolution path, and Ceretax does not offer one.

Provider Comparison: VDA and Back-Filing Capabilities at a Glance

The table below summarizes how each provider handles VDA work, back-filing, and the service model behind it. Avalara offers VDA support through its paid Professional Services tier, so its entry reflects that offering rather than a flat "no." Cells marked "Unconfirmed" lack direct vendor or third-party documentation in the sources reviewed.

Taxwire is the only provider on this list that owns exposure quantification, VDA negotiation, back-filing, and ongoing compliance in-house without handing off a step.

How We Evaluated These Providers

We ranked these providers against five criteria that decide whether a company can resolve historical exposure, not which tool calculates tax fastest.

VDA filing capability came first. A provider either negotiates the agreement with state authorities or it does not. Back-filing support followed, since a VDA without the returns to back it is half a solution. We then separated managed-service providers, where tax professionals own the process, from self-serve software, where you do the work. Pricing transparency mattered next, because a provider that hides VDA work inside an opaque professional services tier costs you more than the sticker suggests. Professional accountability closed the list. We weighed whether a named tax team reviews returns before submission and answers for the outcome.

We included software-only tools that calculate but never file or resolve back exposure. Buyers facing a state notice often mistake a calculation engine for a remediation service, and the two solve different problems. Listing both helps you see where the category boundary actually sits.

FAQs

What is a voluntary disclosure agreement (VDA)? A VDA is a contractual agreement between your company and a state tax authority in which you voluntarily disclose unpaid sales tax before the state contacts you. In exchange, the state caps how far back it will assess tax, typically three to four years, and waives the penalties that would otherwise apply. Interest on the back tax still accrues and remains fully owed, so a VDA reduces the assessment but does not erase the underlying liability.

How do lookback periods work? Without a VDA, a state that finds an unregistered company with nexus can assess tax from the first taxable sale, with no statute of limitations bounding how far back it reaches. A VDA replaces that open-ended exposure with a fixed window. California illustrates the gap directly. Under a qualifying disclosure, the state limits how far back it can assess tax, where the statutory period without a VDA is substantially longer. The shorter window is the core financial benefit of disclosing before the state makes contact.

When is a VDA the right move versus waiting for a state notice? The two paths produce different structural outcomes, and the difference is mechanical, not strategic. If you initiate a VDA before any state contact, you remain eligible for the capped lookback and penalty waiver. If the state contacts you first through a notice, audit, or inquiry, your VDA eligibility closes entirely. From that point the state can apply its unlimited lookback and assess the full penalty exposure with no abatement available. Prior registration in the state and prior contact from its agents both disqualify you the same way.

What does the VDA process look like from start to finish? The process moves through six stages. First, exposure quantification measures how much tax went uncollected across each state. Second, a nexus review confirms where the obligation actually exists. Third, you file the VDA application, often anonymously through a representative. Fourth, the state negotiates the lookback period and terms. Fifth, you complete the back-filings for the agreed period and pay the assessed tax and interest. Sixth, you register and return to ongoing compliance going forward. One point holds across every outcome. Tax you already collected from customers but never remitted to the state stays fully owed regardless of the VDA, because that money was never yours to keep and no penalty waiver touches it.