Not long ago the AI bill was one subscription. Now it's three or four, plus a usage meter that ticks every time a client's project runs. At some point you look at the total and ask whether you should charge clients for AI tools, or keep quietly paying for them yourself.
The short version: don't bill clients for the AI subscriptions you'd pay for anyway. Those are overhead, and overhead belongs in your rate. Do bill for AI costs that exist only because of one client's project, such as metered API usage or a tool they asked you to use, as long as you agreed it in writing before the work started.
Below: the one test that sorts every AI cost into "yours" or "theirs", the arithmetic on why a $20 line item costs more than it earns, whether to add a markup, and wording you can paste into a quote.
Should you charge clients for AI tools? One test decides
Ask one question about each cost: would I still be paying this if this client disappeared tomorrow?
If yes, it's overhead: a cost of being in business, like your laptop, your design software and your internet. Clients pay for overhead through your rate, not as a line on the invoice. If no, it's a project cost, the same kind of thing as stock photos, printing or a domain name bought for one job, and it's fair to bill it.
We didn't make that rule up. It's how lawyers are told to do it, and they have some of the strictest billing rules of any profession. In 2024 the American Bar Association published Formal Opinion 512 on generative AI. Its guidance on costs: a tool that works like part of equipping the office, such as a grammar checker built into a word processor, is overhead and shouldn't be charged to the client unless that was agreed in advance. An AI service that bills per use, run on thousands of contracts for one particular client, is different. There, the actual out-of-pocket cost can reasonably be billed to that client as an expense.
The opinion leans on an older one from 1993, which says a lawyer's business is selling legal services, "not photocopy paper, tuna fish sandwiches, computer time or messenger services." When a professional body has to put tuna fish sandwiches in writing, you can be fairly sure somebody once billed for one.
You're not a lawyer, and that opinion doesn't bind you. But it's a well-tested line, and it sorts AI costs into three groups:
- Subscriptions you use across clients (a chat assistant, a coding assistant, an image generator): overhead. Build them into your rate.
- Metered usage one project runs up (API calls behind a client's chatbot, bulk processing of their files): a project cost. Bill it, at cost or with an agreed markup.
- A tool the client asked for, or one you only bought for their job: a project cost. Bill it or, better, have them buy it.
Why AI subscriptions belong in your rate, not on the invoice
Say you pay for three AI tools at roughly $20 a month each. That's $60 a month, or $720 a year. Spread over 1,000 billable hours, which is about 20 a week, it comes to 72 cents an hour.
Move a $75 hourly rate to $76 and the whole bill is covered, with change. No client will notice the dollar. Every client will notice a line that says "AI subscription: $15".
Putting subscriptions on the invoice causes three problems:
- The split is arbitrary. Four clients, one $60 bill: does each pay $15? What about the month one of them sent you no work?
- It invites an audit of your toolbox. Once tools are on the invoice, which ones you really need becomes the client's business.
- It turns a cost into a discount request. A visible AI line prompts the obvious follow-up: if software did part of the work, why isn't the price lower? We covered why that logic is wrong in should you charge less if you use AI, but it's easier not to start that conversation over $15.
Nobody itemises their laptop or their design software either. AI subscriptions are the same kind of cost, just newer.
When to bill clients for AI costs
There are three situations where passing the cost on is fair, and most clients will expect it:
- Metered usage inside something you built for them. A support chatbot, an automation, a content pipeline: if it calls an AI model every time it runs, the cost rises with the client's usage, not yours. A flat fee can't absorb a number you don't control.
- A big one-off job. Transcribing 300 hours of recordings or sorting 20,000 product descriptions can run up a real bill in a week, for one client only.
- A tool the client chose. If they want the work done in a specific paid tool you wouldn't otherwise have, that's their cost.
For anything ongoing, the cleanest answer is that the client pays the provider directly. They open the account, add their card and give you access, the same way most clients own their own domain and hosting. You never front the money, there's no markup to argue about, and a usage spike lands on their card, not yours. If you stop working together, the thing keeps running without you in the middle.
Should you mark up AI costs you pass on?
If the account has to be yours, you have two honest options: bill the usage at cost, or bill it at cost plus a markup the client agreed to. The only wrong option is a markup nobody mentioned.
At cost is what most clients assume when they see a pass-through line. But "at cost" isn't free for you. You pay the provider first and get repaid weeks later. If the client pays your invoice by card, the payment processor keeps roughly 3% of the pass-through too. And you carry the risk of a month where usage triples.
That's the case for a small handling markup. There's no standard figure. Something like 10% to 15% is easy to justify, and what matters most is that it's written in the quote before the work starts.
One thing to watch: a 15% markup is not a 15% margin. The $12 you added is about 13% of the $92 you billed. Our markup calculator converts between the two.
The ABA opinion draws the same line for lawyers: no surcharge on a passed-through cost unless the client was told, and any discount the provider gives you goes to the client.
Fixed-price projects: estimate the usage, then cap it
On a fixed fee, AI usage comes out of your margin unless you planned for it. Before you quote, run a small sample (50 documents, or a day of test conversations), check what it cost and multiply up. Then write the allowance into the quote: the fee includes AI usage up to a set amount, and anything beyond that is billed at cost, with the client's approval first.
For example, a $1,500 project might include up to $100 of usage. If the real figure is $60, you keep the difference. If it's heading for $150, you send a two-line email before it gets there, not an apology after.
Photo by Kindel Media on Pexels
How to put AI costs on a quote or invoice
Whichever route you choose, say it once, in writing, before the work starts. Three versions you can adapt:
- Built into your rate: "My rates include the software and AI tools I use to do the work."
- Pass-through at cost: "AI usage for this project is billed monthly at cost, with the provider's usage report attached. Estimate: $40 to $80 a month. I'll ask before going over $100."
- Pass-through with a markup: "AI usage is billed monthly at cost plus 15% handling, with the provider's usage report attached. I'll ask before the monthly total goes over $115."
On the invoice, give the pass-through its own line and label it plainly, for example "AI usage (pass-through), September: $80". Don't fold it into your hours. Show dollars and what the usage produced (4,200 support replies, 300 hours transcribed), not tokens, which mean nothing to most clients.
One side effect: an AI line on an invoice tells the client you use AI. If you haven't had that conversation yet, have it before the invoice does it for you. Our guide to telling clients you use AI has wording for that too.
Frequently asked questions
Can I bill a client for my ChatGPT subscription?
Not as a line item, in most cases. A subscription you use across all your work is overhead, like your laptop or design software, so it belongs in your rate. The exception is a tool you bought only for one client's project or one the client asked you to use: that's a project cost, and it's fair to bill it if you agreed it up front.
How do you bill clients for AI API costs?
Give the usage its own line on the invoice, billed at cost or at cost plus a markup the client agreed to, and attach the provider's usage report. Put an estimate and a cap in the quote so nobody is surprised. For anything that runs month after month, it's usually simpler for the client to hold the account and pay the provider directly.
Should I mark up AI costs I pass on to a client?
You can, as long as the markup is stated before the work starts. Most clients assume a pass-through cost is billed at cost, so a hidden markup damages trust when it comes out. A small disclosed handling markup is reasonable, because you pay the provider first, wait to be repaid and lose a few percent to payment fees.
Should the client pay for the AI account directly?
For ongoing usage inside something they'll keep running, such as a chatbot or an automation, yes. They open the account and give you access, the way most clients own their own domain and hosting. You don't front the money, a usage spike lands on their card, and the system keeps working if you stop working together.