How law firms are billing clients for AI
65% of mid-size law firms are absorbing AI costs entirely, not passing them to clients. The reason is not client resistance or ethics rules. It is the efficiency math: a tool that cuts research time in half is hard to bill at full cost, and firms that tried usage-based pass-through are finding that out directly from clients. The model gaining ground is simpler: charge for attorney time spent prompting, reviewing, and correcting AI output, not for the subscription. Most firms have not finished writing that policy.
| What mid-size firms report | Share |
|---|---|
| Absorbing all or most AI costs internally | 65% |
| Using usage-based or matter-level pass-through | 25% |
| Folding AI costs into rates with no separate charge | 15% |
Efficiency kills the pass-through argument
AI makes work faster, and clients can tell. Billing a client the full cost of a tool that cut your attorney's research time in half is difficult to defend. Firms trying usage-based or matter-level pass-through are running into this directly, not as a hypothetical ethics question but as a client objection on an actual invoice. The problem is not the ethics rules or the billing system. It is that the client can do the same math you can.
License fees stay internal; attorney time does not
The model gaining ground is not a line item for subscriptions or tokens. It is attorney time: hours spent prompting, reviewing output, catching errors, and signing off. That framing works because it maps to something the engagement letter already covers, professional judgment applied to a task. License fees do not map to anything the client recognizes as a deliverable. The telling gap: 45% of firms that have added AI billing language to their engagement letters explicitly address how AI-assisted work gets charged, meaning most firms have named the tool without explaining how it shows up on the bill.
Nobody has a finished answer
No firm has a settled policy. Vendor pricing models are still shifting, bar guidance is thin in most jurisdictions, and the efficiency math changes every time a firm renews a subscription. Firms defining the logic now, what counts as AI-assisted work, how it is categorized, how it appears on an invoice, will have a defensible answer when a client asks. The ones waiting for a finished external standard may not.
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