What Karbon does, fairly.
Karbon is the strongest practice management platform in the mid-market CPA segment. The product is well-engineered. The State of AI in Accounting Reports they publish are useful industry references. Karbon AI ships features that genuinely help the average Karbon customer.
If your firm is on Karbon today and the workflows you most want automated are the ones Karbon AI covers, the right answer is to use Karbon AI well. We will tell you that on a diagnosis call. We are not anti-Karbon.
Where the framing shifts for mid-market firms.
The 30-150 pro firm has different leverage points than the 5-30 pro firm. The expensive workflows live in the tax-prep stack: PBC chase, tie-out, advisory deliverable assembly, partner-time reconstruction. Karbon's strength is the practice-management layer above tax-prep. The leverage in your firm's biggest cost lines is below that layer.
This is not a bug in Karbon. It's a segmentation choice. The product was built for a specific segment, and it serves that segment well. Mid-market firms who buy Karbon hoping it will solve compliance leakage discover, around month four, that the bottleneck didn't move.
The pattern we see in twenty-six firm audits.
Twenty-six firms in the $8M-$50M band, audited over the last 18 months. Of those, eleven were on Karbon at the time of the audit. Eight of the eleven reported that Karbon AI had reduced administrative friction in their practice management. That's a real win and we counted it.
The same eight reported that the bigger problems remained: 600-1,200 partner-equivalent hours per season lost to PBC chase, tie-out, and advisory pipeline that didn't ship. Karbon AI hadn't reached those workflows because Karbon AI wasn't designed to.
Three of the eleven told us they were considering canceling Karbon when their renewal came up because the per-seat math at 60-90 pros was not justifying the workflow improvement. Two more were planning to stay because they used Karbon for other reasons (workflow visibility, team standardization) that did justify the cost.
What the math actually looks like.
Karbon at $50/seat/month for 60 pros = $36K/year. Across a 5-year holding period, $180K, plus annual increases.
A custom commissioned build for one workflow (PBC + tie-out + advisory assembly on top of CCH Axcess) runs $90K-$140K fixed-fee, owned at handoff, with maintenance running ~$1,500/month after launch. 5-year cost: $180K-$230K, against 600-1,200 partner-equivalent hours per season recovered.
The right question is not "Karbon vs commission" as a binary. It's "Karbon for the workflows it covers + commissioned AI for the workflows it doesn't." Most of the firms we work with run that combination. Honest comparison here.
What we'd recommend.
If your firm is 5-30 pros, run Karbon. Use the AI features as they ship. You'll get most of what Karbon AI delivers and the per-seat math is fine.
If your firm is 30-150 pros and your tax-prep stack is CCH Axcess + UltraTax or ProSystem fx + Lacerte, run the Tax Season Hours Teardown first. It is 8 minutes and tells you where the actual leakage lives. If the leakage is concentrated in workflows Karbon AI addresses (client communication, generic email triage, basic time-entry suggestions), Karbon is the right answer. If the leakage is concentrated in PBC chase, tie-out, or advisory pipeline, the CCH Axcess Playbook describes what we'd commission instead.
If your firm is 150+ pros, neither Karbon AI alone nor a single commissioned build is enough. You're in the territory where you need an AI roadmap, possibly a Head of AI, and likely a 24-36 month transformation that combines off-the-shelf and commissioned work. The Big Four vs boutique framing applies here.
What we hope you take from this letter.
The framing matters more than the answer. Most managing partners who consider Karbon do so because the alternative seems harder to evaluate. It is harder to evaluate. The diagnostic work is more partner attention than the Karbon sales process is, and the deliverables are less polished than a SaaS pitch deck.
If you're going to spend $36K/year on Karbon for the next five years, spend 8 minutes on the teardown first. If Karbon is the right answer, you'll know. If something else is, you'll also know. Either way, you don't sign a 5-year compounding contract on incomplete framing.