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Six years after Wayfair, sales tax compliance is no longer a niche concern for the occasional multi-state client. It is a standing obligation for nearly every business that sells across state lines — which, in a post-pandemic e-commerce economy, is most of them. And yet a significant portion of CPA firms are still treating sales tax as a reactive service: something they address when a client gets a state notice, rather than a proactive compliance practice they manage systematically.
That gap is a risk problem for clients and a positioning problem for firms. The clients who are not being told about their nexus exposure are accumulating liability. The firms that are not offering this service are creating an opening for a specialist to come in and own part of the client relationship.
This blog examines the real pros and cons of building a sales tax practice in-house, what the post-Wayfair compliance landscape actually demands, where the penalty exposure sits, and when a structured partner arrangement is the better answer.
Before examining whether to build this practice, it is worth being precise about what managing it actually requires. This is the context your clients are operating in, and it is what your team would need to stay on top of.
Every state with a sales tax — 46 in total — now has an economic nexus standard. The common threshold is $100,000 in sales or 200 transactions in a calendar year, but there is significant variation: Texas requires $500,000, some states count transactions differently, and several have eliminated the transaction count requirement entirely. Ohio moved its commercial activity tax threshold from $3 million to $6 million in 2025. Louisiana added SaaS to its tax base in 2025. More than 500 local tax rate changes occurred in 2024 alone.
For a firm managing 20 multi-state clients, that is approximately 920 individual nexus threshold monitoring requirements — each of which needs to be updated when states change their rules. The average CPA firm tracking this manually spends 8 to 12 minutes per client per month on threshold monitoring alone. At 20 clients, that is 32 to 64 hours per month of work that does not bill at the rate it consumes.
Sources: CPA Journal, How Wayfair's Economic Nexus Has Redefined Business Tax Obligations, September 2025; US Tech Automations, Sales Tax Nexus Automation Case Study, April 2026; Zamp, Sales Tax Nexus Tracking Trends, March 2026.
There are genuine business reasons CPA firms have invested in sales tax capabilities. The opportunity is real.
Unlike a one-time audit or a tax return that renews annually, sales tax compliance is a continuous obligation. Registration management, return preparation across multiple states, nexus monitoring as client revenue grows — this work recurs every month, every quarter, and every year. Firms that package this as a managed service own a subscription-like revenue stream that is harder to walk away from than a single engagement.
67% of small business owners would pay $150 to $500 per month for proactive state compliance monitoring, according to CPA Practice Advisor's 2025 client survey. Fewer than 15% of accounting firms currently offer it as a packaged service. That gap is a direct revenue opportunity for firms willing to build the infrastructure.
Source: CPA Practice Advisor, 2025 Client Survey via US Tech Automations ROI Report, April 2026.
Sales tax compliance, done proactively, positions your firm as the client's primary compliance partner — not just their tax preparer. When you are monitoring their nexus thresholds, filing their state returns, and advising them as they expand into new markets, the relationship becomes harder to displace. A client who uses your firm for income tax and goes elsewhere for sales tax compliance has introduced a competitor into their financial life.
E-commerce has created nexus exposure for businesses that have never thought of themselves as multi-state sellers. A manufacturer who starts selling direct-to-consumer online, a SaaS company crossing $100,000 in California revenue, a professional services firm with remote staff creating payroll nexus — these are clients already in your book who have exposure they may not know about. The opportunity to surface that issue is yours first.
Voluntary Disclosure Agreements (VDAs) allow businesses with prior-period nexus exposure to come into compliance with limited lookback periods and penalty waiver in most states. For CPA firms, a nexus review that surfaces historical exposure creates a natural VDA engagement — high-value advisory work that directly protects the client and generates fees that bear no resemblance to a commodity service.
Looking to Offer Sales Tax Compliance to Your Clients — Without Building It Yourself?
We handle multi-state sales tax compliance for CPA firms. Refer the work, deliver it under your brand, or build a practice with us — whatever fits your firm.
Sales tax is one of the most jurisdictionally fragmented compliance areas in U.S. tax practice. The complexity is not conceptual — it is operational. And it scales badly with general knowledge.
Whether a product or service is taxable is not a federal question — it is a state-by-state determination, and the states disagree with each other constantly. Software as a service is taxable in some states, exempt in others, and subject to its own category in a third. Digital goods, professional services, food and beverages, and medical products all have state-specific taxability rules that can change through legislation or administrative guidance with little notice.
A firm building this practice from general knowledge will encounter a client whose product is taxable in 23 states and exempt in 19, and will need to make that determination correctly across all 42. Getting it wrong in either direction — over-collecting or under-collecting — creates liability for the client.
When a nexus event is missed — a client crosses a state threshold without registering and begins collecting obligations — the exposure is not hypothetical. Back taxes typically run 2 to 4 years retroactively. State penalties range from 5% to 25% of tax owed. Interest accrues at state rates of 5% to 12%. Voluntary disclosure program costs run $2,500 to $8,000 per state.
The average total cost of a missed nexus event is $14,800 per state, according to Avalara's 2025 Compliance Risk Report. For a client who crossed thresholds in four states over two years without registering, that is a $59,200 exposure that lands on the client and a conversation about why the firm did not catch it that lands on the partner.
34% of accounting firms reported at least one nexus compliance failure in the prior 12 months. For firms without automated monitoring, this rate is essentially a function of portfolio size and time.
Sources: Avalara 2025 Compliance Risk Report via US Tech Automations; CPA Practice Advisor 2024 survey.
A CPA firm tracking nexus thresholds manually across 30 multi-state clients is managing approximately 1,380 individual threshold monitoring points — each requiring monthly review, updated whenever any of 46 states changes its rules. The AICPA's 2024 practice efficiency survey found firms spending 8 to 12 minutes per client per month on this task alone.
At that rate, the monitoring work for a 30-client multi-state portfolio consumes 48 to 96 hours per month before a single return is prepared. That is staff time that does not bill proportionally to the hours invested, and it is concentrated in exactly the kind of low-leverage, high-attention work that drives experienced people out of the practice.
Firms that do this well use dedicated sales tax compliance platforms — Avalara, TaxJar, Vertex, or similar — to automate threshold monitoring, calculate rates across 13,000+ jurisdictions, and manage multi-state filing calendars. Those platforms carry meaningful subscription costs. For a firm doing sales tax work for eight clients, the per-client technology cost rarely justifies the fee structure.
The firms making sales tax profitable are the ones spreading platform costs across a large enough client base to amortize them — typically 25 or more active multi-state clients. Below that volume, the technology cost and the manual labor cost together make the practice economically marginal.
Sales tax compliance is a volume business. The economics work when the infrastructure cost spreads across enough clients. They rarely work when it does not.
The decision framework here is similar to EBP audits and financial statement audits: below a certain volume, the infrastructure cost per engagement makes in-house delivery economically difficult to justify. Above that volume, the recurring revenue and client stickiness make it one of the more attractive practices a CPA firm can build.
The practical threshold for in-house viability is approximately 20 to 25 active multi-state compliance clients. Below that, a referral or white-label arrangement with a specialized partner typically produces better client outcomes and better margins for the referring firm. Above that, with the right technology and a dedicated team, the practice becomes a recurring revenue engine.
The other consideration is the direction your firm is heading. Firms building toward advisory and planning are often better served by referring sales tax compliance to a partner and staying focused on the work that requires their judgment. Firms building toward managed compliance services at scale — monthly bookkeeping, payroll, sales tax, income tax all bundled — should consider building this capability seriously.
Three models cover the range of where CPA firms sit on this decision:
MYCPE ONE has been working with CPA and accounting firms for over 10 years. 200+ partner firms, 3,000+ professionals across 40+ offices in two countries, 10,000+ clients supported. The sales tax compliance infrastructure — monitoring tools, multi-state filing processes, VDA expertise — is already built. Firms that partner with MYCPE ONE do not build from scratch. They deliver a service their clients need, immediately, without the overhead of building it themselves.
Your Clients Need Sales Tax Help. We Can Make Sure They Get It Through Your Firm.
MYCPE ONE supports CPA firms with sales tax compliance delivery — you keep the client relationship, we handle the multi-state complexity.
Sales tax compliance after Wayfair is not a niche service. It is a standing obligation for most multi-state businesses, it carries quantifiable penalty exposure when it goes wrong, and 34% of accounting firms are still missing nexus events manually. The clients who need this service are already in your book. The question is whether you are managing it for them or whether someone else eventually will.
For firms with fewer than 20 multi-state compliance clients, the economics of in-house delivery are difficult. For firms building toward managed compliance at scale, sales tax is one of the most attractive recurring service lines available. In either case, the decision should be made deliberately — not by default.
Back taxes (2-4 years retroactive), state penalties of 5-25% of tax owed, interest at 5-12%, and voluntary disclosure fees of $2,500-$8,000 per state. Avalara's 2025 Compliance Risk Report puts the average total at $14,800 per state before reputational costs.
A VDA allows a business to come into compliance proactively, with most states offering a limited lookback period (typically 3-4 years) and penalty waiver. Filing a VDA before a state contacts the business is the key requirement. Once a state initiates contact, the VDA window typically closes.
$100,000 in annual sales or 200 transactions is the most common standard, adopted from the original South Dakota v. Wayfair framework. Texas requires $500,000. Several states have eliminated the transaction count requirement. Ohio raised its commercial activity tax threshold to $6 million in 2025. Thresholds change, which is why monitoring is required.
Avalara, TaxJar, and Vertex are the most widely used platforms for multi-state nexus monitoring and rate calculation. They integrate with most accounting and ERP systems. The choice of platform depends on client volume, transaction complexity, and industry.
It depends entirely on the state. SaaS is taxable in some states, exempt in others, and subject to a separate digital services category in a third group. Louisiana added SaaS to its tax base in 2025. This is one of the fastest-changing areas in state tax law and one of the most common sources of classification errors.
Christopher is the Director of Client Relations and Business Development at MYCPE ONE, a leader known for his energy and people-first approach. Chris leads from the front mentoring teams, driving growth, and building lasting client relationships. With over a decade of experience in sales, coaching, and business strategy, he has helped 5,000 CPAs nationwide overcome challenges and discover new opportunities. Chris is a familiar presence at major accounting conferences, representing MYCPE ONE and shaping meaningful industry partnerships. Passionate about leadership and professional growth, he continues to inspire teams and professionals to reach their highest potential.
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