Outsourcing multi-state sales tax compliance for CPA firms works best when the provider handles the volume work (nexus monitoring data, registrations, return preparation, exemption certificate files and first-pass notice responses) and the firm keeps nexus conclusions, client advice and final sign-off. The firm stays responsible to the client and to each state, so the outsourcing model has to be built around review points and a clean audit trail.
This guide sets out what CPA firms can outsource in multi-state sales tax compliance, how the monthly workflow runs, which controls to require, where Section 7216 applies to sales tax data, and an illustrative capacity and cost example for a 30-client sales tax practice.
Since South Dakota v. Wayfair (2018), physical presence is no longer the test for whether a state can require a remote seller to collect. The Court held that "the physical presence rule of Quill is unsound and incorrect" and upheld a South Dakota law that applied to sellers delivering "more than $100,000 of goods or services into the State or engage in 200 or more separate transactions." South Dakota has since narrowed its own rule: the South Dakota Department of Revenue confirms that from 1 July 2023 its remote seller criteria "no longer includes the 200 or more transactions threshold." Other states have written their own economic nexus rules, each with its own threshold, measurement period and registration deadline.
For a CPA firm, that turns one ecommerce client into a set of filing obligations that change as the client grows. A client selling into 12 states may have monthly returns in some, quarterly in others and annual in the rest, each with its own portal and its own due date. The work is repetitive and deadline-driven, and it rarely carries fees that justify senior staff time. Our guide to economic nexus for growing businesses explains how thresholds are measured.
The thresholds differ even among neighbouring states, which is why tracking needs to be state by state:
| State | Remote seller threshold | Measurement period | Source |
|---|---|---|---|
| South Dakota | Over $100,000 of gross sales (200-transaction test dropped from 1 July 2023) | Previous or current calendar year | SD Department of Revenue |
| Texas | $500,000 total Texas revenue safe harbor | Preceding twelve calendar months | Texas Comptroller |
| New Jersey | Over $100,000 gross revenue or 200+ separate transactions | Current or prior calendar year | NJ Division of Taxation |
The Texas Comptroller states that "Remote sellers with total Texas revenue of less than $500,000 in the preceding twelve calendar months are not required to obtain a tax permit," and that the revenue count "includes sales for resale and sales to exempt entities." New Jersey uses the $100,000 or 200-transaction test across "the current or prior calendar year." For rates, registration and filing detail, see our Texas sales and use tax guide, our New Jersey sales tax guide and our Maryland sales tax guide.
The useful split is between work that follows a documented procedure and work that requires a professional conclusion. A trained offshore or outsourced team can carry most of the first category. The firm keeps the second.
The provider can pull sales by ship-to state from the ledger, ecommerce platforms and marketplace reports, then compare each state's trailing totals to its threshold every month. The output is a nexus tracker showing where the client is under, approaching or over each threshold, with the date it was crossed. Marketplace sales need their own column, because some states count them toward the threshold even though the marketplace collects the tax. The firm's manager decides whether the client has nexus and when registration is required, and whether past exposure calls for a voluntary disclosure agreement.
Once the firm approves a registration, the provider can prepare the state application, gather entity documents and track the permit number, assigned filing frequency and portal credentials. In Texas, a remote seller over the safe harbor must begin collecting "no later than the first day of the fourth month after the month" it crosses $500,000, so the registration task needs a due date in the tracker the moment the threshold is crossed. The Streamlined Sales Tax Governing Board reports that twenty-four states have adopted its simplification measures, including a "Central, electronic registration system for all member states," which can shorten the work for clients with nexus in several member states.
This is the largest block of hours. The provider reconciles gross sales from the platform reports to the general ledger, separates exempt and marketplace sales, applies jurisdiction rates and prepares each return in the state portal or in the client's sales tax software. If the client already uses a calculation engine, the provider works from its reports. Our comparison of sales tax automation software covers those tools, and outsourcing sits alongside them. Software calculates the tax, and people still reconcile the data, chase exceptions and file.
The provider can maintain the certificate database: matching each exempt sale to a certificate on file, checking that the certificate form matches the state, logging expiry dates and sending renewal requests before they lapse. Missing certificates are a common way exempt sales turn into assessed tax during an audit.
States send notices for late or missing returns, payment mismatches and rate errors. The provider can log every notice, match it to the filing history, draft a response with supporting reconciliations and track the response deadline. Anything involving an assessment, a penalty waiver request or an audit goes to the firm. Our article on how to handle a sales tax audit covers that stage.
Nexus conclusions, taxability calls on new products or services, voluntary disclosure strategy, client communication about exposure and the final approval of every return stay in-house. The firm also owns the engagement letter, the client consent forms and the decision to file.
A dependable monthly cycle has five stages. The specific days below are guidance, and firms should set them around each client's earliest state due date.
Our article on the multi-state sales tax workflow for ecommerce clients goes deeper into platform reports and marketplace data.
The controls below are the minimum we would expect before any client data moves. Each one should appear in the service agreement, with the review points written into the service level clauses.
| Control | What it means in practice |
|---|---|
| Single filing calendar | One tracker listing every client, state, frequency, due date, preparer, reviewer and status |
| Maker and checker | The person who prepares a return never approves or files it |
| Reconciliation tie-out | Every return ties to the general ledger, with variances above a set amount explained in writing |
| Filing authority | Portal payments and submissions happen only after the firm's recorded approval |
| Certificate audit | A quarterly sample of exempt sales is matched to valid certificates |
| Notice log | Every notice is logged within one business day with an owner and a response date |
| Access control | Named user accounts, multi-factor authentication and removal of access when staff leave |
The data security side matters because CPA firms are covered by the Gramm-Leach-Bliley Act. The IRS reminds tax professionals that under this law "tax and accounting professionals are considered financial institutions and must implement a data security plan," and that covered firms "must report certain security events affecting 500 or more people to the FTC, generally within 30 days of discovery." Your written information security plan should name the provider, describe its access and set out how incidents are reported to you. A vendor risk assessment covering SOC 2 and ISO 27001 is the usual way to document that review.
Section 7216 is narrower than many firms assume. The regulations define a tax return as "any return (or amended return) of income tax imposed by chapter 1 of the Internal Revenue Code," according to Treas. Reg. § 301.7216-1. A state sales tax return is outside that definition.
The rule still reaches sales tax work in a common situation. Many CPA firms prepare the client's federal income tax return and also handle its sales tax. Ledgers, trial balances and other information the client furnished for the income tax engagement are tax return information. Under Treas. Reg. § 301.7216-2(k), using that information to prepare a state tax return is permitted, but disclosures for that purpose follow the same rules as other disclosures. Those rules require consent for offshore disclosure. The exception for other preparers in paragraph (d) covers only preparers located in the United States, and paragraph (c) states that where the firm's own staff member "is located outside of the United States or any territory or possession of the United States, the taxpayer's consent under § 301.7216-3 prior to any disclosure is required."
In practice, firms take one of two approaches. Some collect sales tax data under a separate engagement so it is never furnished for income tax preparation. Others obtain a Section 7216 consent from every client whose data an offshore team will see. The second is simpler to administer when the same team supports both engagements. Violations carry a civil penalty of "$250 for each prohibited disclosure or use, not to exceed a total of $10,000 for a calendar year," and a criminal misdemeanor penalty. Our guide to Section 7216 consent covers the consent form requirements. Review your approach with your own counsel, because state confidentiality rules and professional ethics rules apply on top of Section 7216.
The figures below are illustrative assumptions for planning, and they are not quotes, benchmarks or Madras Accountancy prices.
A firm supports 30 sales tax clients:
That is 664 returns a year. Assume 1.25 hours of preparation per return (including reconciliation and certificate matching), 0.25 hours of review, and a loaded in-house cost of $65 an hour.
| Item | All in-house | Outsourced preparation |
|---|---|---|
| Preparation hours | 830 (in-house) | 830 (provider) |
| Onshore review hours | 166 | 166 |
| Onshore coordination hours (0.1 per return) | 0 | 66.4 |
| Total onshore hours | 996 | 232.4 |
| Onshore cost at $65/hour | $64,740 | $15,106 |
| Provider cost at an assumed $25/hour | $0 | $20,750 |
| Total annual cost | $64,740 | $35,856 |
Under these assumptions, the firm saves $28,884 a year and frees 763.6 onshore hours for nexus reviews, voluntary disclosures and advisory work. The result is sensitive to the provider rate and to how much coordination time the firm really spends, so rerun it with your own numbers. Our comparison of dedicated staff vs per-return pricing explains how the pricing model changes the math.
Missed deadlines are the other side of the calculation. The Texas Comptroller applies a 5% penalty when tax is paid "1-30 days late" and a 10% penalty when it is "over 30 days late," plus "an additional penalty of $50.00 for each late report." On an illustrative $12,000 monthly Texas return, filing and paying 10 days late costs $650 in penalties ($600 plus $50), and filing and paying 31 days late costs $1,250 ($1,200 plus $50), before any interest.
Start with one group of clients who sell through the same platform and file in a similar set of states. Write the intake checklist and the review checklist before the first handoff, and run the provider in parallel with your own staff for one or two filing cycles. Track three measures from the start: days from data receipt to filing, the number of returns sent back by reviewers, and notices received per quarter. Expand to the next client group once those measures are steady.
What parts of multi-state sales tax compliance can a CPA firm outsource? Data collection, reconciliation, nexus threshold tracking, registration paperwork, return preparation, exemption certificate management and notice logging can all be outsourced. Nexus conclusions, client advice and final approval of returns should stay with the firm.
Does Section 7216 apply to sales tax returns? The regulations define a tax return as a federal income tax return, so a sales tax return is outside the definition. If the data used for sales tax came from your income tax engagement, it is tax return information, and disclosing it to a team outside the United States requires client consent.
Do outsourced teams file returns and make payments? They can, but only after the firm's reviewer approves each return. Many firms keep payment authority in-house and let the provider submit returns once approval is recorded.
Does sales tax software remove the need to outsource? No. Software calculates rates and can file in many states, but someone still has to reconcile platform data to the ledger, maintain certificates, track thresholds and answer notices. Outsourcing covers that work.
How long does it take to move sales tax work to an outsourced team? For one client group, plan on one or two filing cycles of parallel running before the provider prepares returns on its own, then expand group by group.
Madras Accountancy supports CPA firms with bookkeeping, tax preparation, sales tax compliance support, audit support and CFO-level advisory, working under your firm's review and sign-off. To discuss how your sales tax workload could be structured, contact our team.
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