How to Price a CAS Engagement That Includes Tax Research
The most common pricing mistake in Client Advisory Services (CAS) engagements is underestimating research time. This applies specifically to firms where CAS and tax work under the same roof, which is most small and mid-sized practices. When you're handling bookkeeping, payroll, and advisory alongside tax compliance and planning, the tax research questions that surface during CAS work are real and recurring. A typical CAS client generating 5 to 10 tax-related questions per month consumes 2.5 to 5 hours of research at 30 minutes per question. That time rarely appears on an invoice. It blends into "advisory," "client calls," and "planning," which makes it invisible until your margin report tells you the engagement lost money. The fix is straightforward: build research cost into the engagement price from the start, using a model that accounts for both the predictable baseline and the inevitable spikes.
Why CAS Research Time Disappears
Traditional tax compliance work has a natural boundary. You prepare the return, you deliver it, you bill for it. Research that happens during return prep is part of the deliverable, even if you don't line-item it separately.
CAS engagements don't have that boundary. You're on retainer. The client calls with a question about whether their new equipment purchase qualifies for bonus depreciation, or whether their contractor reclassification triggers payroll tax obligations, or how the pass-through entity tax election works in their state. Each question feels small. Each one takes 20 to 45 minutes to research properly when you're working from primary sources.
The AICPA's surveys on CAS adoption consistently show advisory services growing faster than compliance. But the same data shows that firms frequently underprice these engagements, and research time is the gap most don't measure. You quoted a monthly retainer based on the bookkeeping, payroll review, and quarterly planning calls. You didn't budget for the 7 research questions that came in during February, or the 12 that came in during March when the client started a new venture.
This is the same dynamic that affects cost per return, except it's worse because CAS engagements run 12 months instead of one filing season. The cumulative leak is larger.
Three Pricing Models for CAS Research
Every CAS engagement with a research component ends up in one of three structures. Each has a specific failure mode.
Model 1: Hourly Billing for Research
You bill CAS advisory at your standard rate, tracking research time separately. The client pays for what you use.
The math looks clean. If a question takes 35 minutes at $300/hour, that's $175 billed. The client sees the charge, you recover the cost.
The failure mode is client friction. When a CAS client gets an invoice showing 4.5 hours of "tax research" on top of their monthly retainer, the conversation gets uncomfortable. They expected the advisory relationship to cover their questions. You expected to bill for the time. Nobody wrote it down clearly enough.
This friction creates a perverse outcome: you start under-reporting research time to avoid the conversation. You round 35 minutes down to 15. You skip the timer on "quick" questions that actually took 20 minutes. The billable-hour economics of tax questions show that practitioners routinely absorb 30% to 50% of their actual research time rather than bill for it. Hourly billing only works if you actually bill the hours, and most practitioners don't.
Model 2: Fixed Fee with Research Cap
You set a monthly retainer that includes a defined number of research questions. "Your $2,500/month CAS engagement includes up to 5 research questions. Additional questions billed at $150 each."
This is the most common structure I see in practice. It's predictable for the client, and you've acknowledged that research is part of the engagement rather than pretending it doesn't exist.
The failure mode is the incentive structure. When you're on question 4 of 5 and the client asks something that requires digging into Treas. Reg. 1.6662-4 substantial authority analysis across three IRC sections, you feel the cap breathing down your neck. Do you spend 60 minutes doing it right, or do you spend 15 minutes giving a surface-level answer that technically counts as one question?
The cap creates pressure to under-research. That pressure is exactly backward. CAS clients pay you for thorough advisory work. If the pricing model punishes thoroughness, the model is broken, not the practitioner.
The other problem is defining "question." Does a client email asking about estimated tax payments count? What about a 10-minute call that turns into a 45-minute research exercise about state nexus? If the client thinks they've asked one question and you've counted three, the cap becomes a source of conflict rather than clarity.
Model 3: Bundled Subscription (Research Tool Baked In)
You set a flat monthly retainer that includes unlimited advisory questions. Your research tool cost is a line item in your engagement economics, not a variable passed to the client. The client pays one number. You manage the research cost by controlling your time-per-question.
This is the model that aligns incentives. When research takes less time, your margin goes up. You're not penalized for thoroughness, and you're not tempted to under-bill. The client gets what they're paying for: an advisor who answers their questions without nickel-and-diming for each one.
The math only works if your per-question research cost is low enough that the retainer absorbs it comfortably. That's where research speed becomes a margin lever rather than just a convenience.
The Margin Math: 30 Minutes vs. 5 Minutes
Here's a CAS engagement that's representative of what I see in small business advisory. The client is an S-Corp owner with a bookkeeping team handling day-to-day transactions. You provide monthly close review, quarterly planning calls, and year-end tax planning, plus you answer their tax questions as they come up.
Engagement parameters:
- Monthly retainer: $3,000
- Direct costs (your time on bookkeeping review, planning calls, return prep coordination): 6 hours/month
- Research questions: 8 per month (average across the year, with spikes in Q4 and Q1)
- Your effective rate: $300/hour
At 30 minutes per question (traditional research):
- Research time: 4 hours/month
- Total time: 10 hours/month
- Effective hourly rate: $300 ($3,000 / 10 hours)
- Your margin after time cost: $0
You're breaking even. The research time ate your margin entirely. And this assumes you don't go over 8 questions in any given month, which you will in Q4 when the client needs year-end planning guidance.
At 5 minutes per question (AI-assisted research):
- Research time: 0.67 hours/month
- Tool cost: ~$66/month (Solo Practitioner plan, amortized)
- Total time: 6.67 hours/month
- Revenue net of tool cost: $2,934
- Effective hourly rate: $440
- Your margin after time cost: $934/month
Same engagement. Same retainer. Same client. The only variable is how long each research question takes. The difference is $934/month, or $11,208/year, on a single CAS client.
Scale that across 10 CAS clients and the annual margin difference is over $100,000. That's not a theoretical number. It's the direct consequence of research speed on fixed-fee advisory work.
What the Research Cap Should Cover
If you go with Model 2 (fixed fee with cap), the cap needs to reflect real question volume, not wishful thinking. Track your CAS research for 90 days before setting a number. Most firms discover that their "5 questions per month" client actually generates 7 to 9 when you count the quick calls, the forwarded articles asking "does this apply to us?", and the quarterly planning questions.
Set the cap at the 75th percentile of your observed volume, not the average. A client who triggers overage charges three months in a row needs a retainer adjustment, not a bigger invoice.
The Regulatory Baseline You're Pricing For
CAS engagements that include tax advisory or return preparation carry the same professional standards as standalone tax work. Treas. Reg. 1.6694-1 defines the preparer due diligence requirements that apply whether the research question comes from a CAS retainer or a one-off engagement. You can't short-change research quality because you underpriced the engagement.
Treas. Reg. 1.6662-4 establishes the substantial authority standard for disclosed positions. If your CAS client takes a position on their return based on your advisory work, the research supporting that position needs to meet the same bar as any other return. The engagement structure doesn't reduce the professional obligation.
When CAS engagements involve third-party research tools, Treas. Reg. 301.7216-1 through 301.7216-3 govern the disclosure and use of tax return information. If the tool processes client data, the engagement letter should address how that data is handled. This applies to any technology in the CAS workflow, not just research tools.
These requirements create a floor on research time. You can't price an engagement assuming zero research. The question isn't whether to include research cost. It's how to include it efficiently.
Choosing the Right Model for Your Practice
The best pricing model depends on your volume, your mix, and your research speed.
Hourly billing works if your CAS engagements are genuinely unpredictable, your clients understand the structure, and you actually bill the hours. Most practitioners should avoid it.
Fixed fee with cap works for larger firms where the engagement scope is well-defined and the cap is realistic. If you can predict question volume within 20%, this model gives you enough structure without excessive rigidity.
Bundled subscription works best for solo practitioners and small firms where the retainer is the relationship. This model rewards investing in faster research tools because every minute saved goes directly to your margin. It also simplifies the client conversation: one fee, one relationship, no surprises.
If you're deciding whether to handle research in-house or outsource it, the CAS pricing model should factor into that decision. Outsourced research at $100 to $150 per question sounds predictable, but at 8 questions per month, you're spending $800 to $1,200 on research alone.
The solo CPA guide covers the workflow of integrating AI research into daily practice. Once research takes 5 minutes instead of 30, the bundled model becomes viable for engagements that couldn't support it before.
Price the Research or It Prices You
Every CAS engagement includes research. The only question is whether you've accounted for it or you're absorbing it. Track your questions for a month. Time each one. Multiply by your rate. That number is either in your retainer or it's coming out of your margin.
We built Tax Orator to make the bundled model work by reducing per-question research time to the point where fixed-fee advisory is profitable even at 10 or more questions per month. The pricing page has the numbers. The math is clear enough that the decision makes itself.