Billing for AI: How California Attorneys Charge for AI-Assisted Work Without Crossing Rule 1.5
9/30/20264 min read
Billing for AI: How California Attorneys Charge for AI-Assisted Work Without Crossing Rule 1.5
AI can compress a three-hour research task into one. That's the promise — and it's also where the fee problem starts. If a task now takes a third of the time, what can you actually bill the client? Can you pass along your AI subscription? Do you have to say anything at all?
California attorneys have a clear framework for answering these questions, but it lives across two sources that are easy to conflate. Your binding rule is California Rule of Professional Conduct 1.5. The most detailed guidance on how billing duties apply to AI is ABA Formal Opinion 512 — influential and worth following, but persuasive authority in California, not controlling. Here is how the two fit together, and how to bill AI-assisted work cleanly.
The California rule vs. the ABA framing
California Rule 1.5 prohibits charging an unconscionable or illegal fee, and it lists factors that bear on whether a fee crosses that line. That is a different formulation from ABA Model Rule 1.5, which uses a reasonable-fee standard. The distinction matters when you read national commentary: most AI-and-fees writing, including ABA Formal Opinion 512, is built on the ABA's reasonableness language.
The practical takeaway is that the underlying billing-integrity principles line up regardless of which standard applies. Bill for time actually worked. Charge expenses at actual cost. Explain the basis of your charges. Those hold under California's rule and under the ABA framing alike — and they are exactly where AI creates new questions.
Hourly billing: you bill the time you spend, not the time you saved
This is the rule that trips up the most firms. Under ABA Formal Opinion 512, a lawyer who bills hourly must bill only for actual time spent — even when AI makes the work dramatically faster. If a task that used to take three hours now takes one, you bill one. Efficiency gains belong to the client, not to a padded timesheet.
The opinion's own example is useful: if you use a generative AI tool to draft a pleading and spend fifteen minutes entering the relevant information, you may bill that fifteen minutes plus the time you spend reviewing the draft for accuracy and completeness. What you generally may not bill is the time you spend learning how to use the tool in the first place — that's the cost of maintaining your own competence, not client work.
Flat and contingent fees: revisit your assumptions
Flat fees aren't a loophole. If you set a flat fee against pre-AI assumptions about how long the work would take, and AI now compresses that work substantially, the original figure may no longer hold up — under California's unconscionability lens or the ABA's reasonableness factors. The fix isn't complicated: price the value and the outcome deliberately, and don't rely on a number that quietly assumes labor AI has eliminated. The same discipline applies to contingent arrangements, where the factors bearing on the fee still apply.
Expenses: overhead vs. pass-through
Whether you can charge a client for an AI tool as an expense turns on how you pay for it. Drawing on longstanding guidance (ABA Formal Opinion 93-379, carried forward by Opinion 512), the analysis breaks down cleanly:
A tool you license on a flat subscription and use across many matters is generally firm overhead — the cost of doing business, not a separate line item. A third-party AI service you pay for on a per-use basis for a specific matter may be billed to the client as an expense, but only at your actual cost, with no surcharge or markup. When in doubt, ask whether the charge reflects a real, matter-specific out-of-pocket cost or simply your cost of being equipped to practice.
Communication: when the fee itself triggers disclosure
Fee treatment connects directly to your communication duties. Among the situations where AI use should be disclosed to a client is when that use affects the reasonableness — or, in California, the propriety — of the fee charged. If AI materially changes what you bill or how, that's a conversation to have, ideally in your engagement agreement and preferably in writing. Explaining the basis of your charges up front is both a professional-responsibility expectation and the simplest way to avoid a fee dispute later.
A short billing-hygiene checklist
Adopt a written firm position on AI billing so these calls aren't made ad hoc:
State plainly that hourly time is billed as worked, never inflated to pre-AI norms. Confirm that no one bills clients for time spent learning AI tools. Classify each approved tool as overhead (subscription) or pass-through (per-use), in writing, so expense treatment is consistent. Bill any pass-through cost at actual cost, without markup. Put your AI-and-fee position into your engagement letter, and flag when AI use is significant enough to warrant a client conversation.
FAQ
Can I bill hourly for the time I saved using AI? No. Hourly billing must reflect time actually spent. If AI shortens the work, the client benefits from the shorter time.
Can I charge clients for my AI subscription? Generally not as a separate expense — a firm-wide subscription is typically overhead. Per-use third-party services tied to a specific matter may be passed through at actual cost, without surcharge.
Can I bill for learning to use an AI tool? No. Time spent getting up to speed on a tool is part of maintaining competence, not billable client work.
Do I have to tell clients I'm using AI to keep my fee proper? Disclosure is expected when AI use affects the fee, among other triggers. Building your AI-and-fee approach into the engagement agreement handles this cleanly.
Which standard governs my fees in California — reasonable or unconscionable? California Rule 1.5 uses an unconscionable-fee standard. ABA guidance framed around "reasonableness" is persuasive here, not binding, but the practical billing principles align.
Clean AI billing is mostly a documentation problem — get your policy right once, and the day-to-day calls get easy. We help California firms build an AI-and-fees policy that fits their engagement letters and their billing model. Reach out if you'd like yours reviewed.