What questions should I ask a CPA or sales tax consultant before hiring them?

Sales tax advisory is a specialized field. A generalist CPA who files business returns and occasionally handles a state audit is not the same as a SALT specialist who manages multi-state nexus programs for ecommerce brands. The questions below separate the two quickly.

Questions about experience and specialization

“How much of your practice is dedicated to state and local tax?”

The answer should be “most of it” or “all of it.” A firm where SALT is 10% of revenue alongside income tax preparation, bookkeeping, and financial statements doesn’t have the institutional depth you need. Look for advisors whose practice is SALT-focused.

“What size ecommerce brands do you typically work with?”

If the advisor’s typical client is a $500K sole proprietor or a $500M public company, neither is a good fit for a $15M ecommerce brand. You want an advisor who works regularly with businesses at your scale, they’ll know the right questions to ask and won’t over- or under-engineer the compliance program.

“Do you have experience in [your product category]?”

Product taxability is category-specific. An advisor who regularly works with software companies may not know the nuances of food and beverage taxability. An advisor focused on manufacturing may not be current on SaaS nexus rules. Match specialization to your actual products.

“Have you worked with brands selling through Amazon, Shopify, and multiple marketplaces?”

Multi-channel ecommerce has specific complexity, marketplace facilitator rules, FBA nexus, 1099-K reconciliation. An advisor who hasn’t worked with this channel structure will spend billable time getting up to speed on issues that an experienced ecommerce SALT advisor handles routinely.

Questions about specific capabilities

“Describe a multi-state VDA you’ve managed recently.”

Ask for specifics: how many states, did they use the MTC voluntary disclosure program, how long did it take, what were the outcomes? A credible advisor gives you a specific answer with process details. A general “yes we do VDAs” answer is not enough.

“Have you used the MTC voluntary disclosure program?”

The Multistate Tax Commission offers a coordinated voluntary disclosure program covering 39 states in a single application, with anonymous disclosure until terms are accepted. An advisor without hands-on MTC experience will handle a multi-state VDA less efficiently, and may file individual state VDAs sequentially rather than concurrently, adding months and cost.

“Can you represent clients in state sales tax audits?”

Audit representation is a specific competency. Ask whether they’ve handled audits in the states where your risk is highest (California, New York, Texas), and ask for general color on the audit process in those states. An advisor with real audit experience will describe the state auditor relationship, documentation requirements, and settlement approaches from experience.

“Can you write product taxability opinions?”

Written opinions on ambiguous product taxability positions serve as good-faith documentation in audits. Not every advisor writes formal opinions, some give informal guidance. For brands with genuinely ambiguous products (SaaS, digital goods, food adjacent to supplements, etc.), a written opinion is worth having.

Questions about engagement structure

“Who will actually work on my account day-to-day?”

At many advisory firms, the partner or senior advisor sells the engagement and junior associates do the work. Know who you’re actually buying access to. If the advisor you’re interviewing won’t be your primary contact, ask to meet the person who will be.

“What does the engagement cover and what’s an add-on?”

Get explicit clarity on what’s in the retainer vs. what triggers additional billing. Common add-ons: audit representation (typically separate), new-state nexus analyses (should be included in a reasonable retainer), VDA filings (typically project-priced separately), product taxability opinion letters (often hourly or flat-fee per opinion).

“What’s your response time on questions?”

Sales tax decisions sometimes have timing consequences: a nexus question that delays registration creates exposure. Know what to expect: same-day for urgent questions? 48-hour standard turnaround? Weekly check-ins? Align expectations before engaging.

“Can I see a sample engagement letter?”

Review the scope, billing terms, liability limits, and termination provisions before signing. Most SALT advisor engagements limit liability to fees paid (standard for professional services) but the scope definition matters. Unclear scope leads to disputes about what’s included.

Red flags

• Guaranteeing audit outcomes: no advisor can guarantee an audit result; any who do are misrepresenting their service
• Unfamiliarity with the MTC program for multi-state VDA work
• Quoting only by hour with no project estimate: makes it impossible to budget
• No ecommerce clients at your scale: you don’t want to be someone’s first mid-market ecommerce engagement
• Generalist practice with SALT as a side service: depth matters in a specialized field