How to connect Claude to Mighty
Claude is an AI assistant made by a company called Anthropic. When you connect it to Mighty, you can ask it questions about your company in plain words, and it reads the answer from your own figures. It can also prepare work for you to check, such as a draft invoice.
This guide covers the Claude website (claude.ai) and the Claude desktop app. If you use Claude Code, the version of Claude that runs in a terminal, read How to connect Claude Code to Mighty as well.
What you need first
- A Claude account. You can add a connection like this on any Claude plan. On the free plan you can add 1.
- About 5 minutes.
If your Claude account belongs to a Team or Enterprise plan, an owner of that account adds the connection for everyone. The Common questions section at the end of this guide explains how.
How the connection works
You link the two with an API key. An API key is a long password that lets another app into your Mighty company. You create the key in Mighty, then paste it into Claude.
In Claude, the link is called a connector. A connector is a setting that tells Claude where another service lives and how to get in.
A key works for 1 company only. If you look after more than 1 company in Mighty, create a key in each company and add a connector for each one.
What Claude can do in Mighty
| Area | What Claude can do | Can it change your accounts? |
|---|---|---|
| Dashboard | Read your bank balance, profit, tax estimates, dividends available and unpaid invoices. It can also refresh those figures. | No. |
| Reports | Read your profit and loss report (your income and costs), your balance sheet (what the company owns and owes) and your trial balance (the balance on every account), for any period. | No. |
| Sales invoices | List and read your sales invoices (the bills you send customers so they pay you), and create a new one. | A new invoice is saved as a Draft unless you ask Claude to raise it. A raised invoice counts in your accounts straight away. |
| Bank transactions | Look through the transactions waiting for you, read the receipts attached to them, and suggest what each one was for. | No. Claude can only save a suggestion as a draft. You approve each one in Mighty. |
| Mileage | List your mileage claims (business journeys in your own vehicle that the company pays you back for), look up the distance between 2 places, and record a new claim. | Yes. Mighty has no draft mileage claim, so a claim Claude records counts in your accounts straight away. To remove one, delete it on the Mileage Claims screen. |
Claude cannot approve a bank transaction, delete anything, pay anyone or send anything to HMRC (the UK tax authority).
Things you can ask
- "What is my bank balance in Mighty?"
- "Which of my invoices are overdue, and how much do they add up to?"
- "Show me this year's profit and loss next to last year's."
- "Create a draft invoice to Acme Ltd for 3 days of consultancy at £600 a day."
- "Go through my bank transactions that still need sorting, read the receipts and save a draft for each one."
Claude can make mistakes. Check a draft before you approve it, the same way you would check work from a new member of staff.
Using the Claude desktop app
The steps are the same in the desktop app as on the website. The connector belongs to your Claude account, so you add it once. If you added it on the website, open Customize, then Connectors in the desktop app and check that Mighty is listed before you add it again.
Turning the connection off
To stop Claude reaching your company, go to Company Settings, open the Other tab and select API Keys. Select Revoke next to the key, then confirm.
The key stops working straight away. You cannot undo this, but you can create a new key at any time. Revoke a key as soon as you stop using it, or if anyone else may have seen it.
You can also remove the connector in Claude, under Customize, then Connectors. Removing it there does not revoke the key, so revoke the key in Mighty as well.
Common questions
What if I lost my key, or closed the page before copying it?
Mighty shows a key once and does not store it in a form anyone can read, so it cannot show it again. Revoke that key and create a new one.
What if I cannot see Request headers in Claude?
Anthropic is still switching this option on for Claude accounts, so some accounts do not have it yet. Without it, Claude has no place for your key and the connector cannot sign in to Mighty. Until it appears, you can connect using Claude Code.
What if Claude says it cannot connect?
Check these 3 things in the connector's settings in Claude:
- The address is exactly
https://api.mightyaccounting.com/mcp. - The header name is exactly
X-Api-Key. - The header value is your whole key, with no spaces before or after it.
Then check in Mighty that the key still shows Active. If it shows Revoked, create a new key and put it in the connector.
What if my Claude account is on a Team or Enterprise plan?
An owner of the Claude account adds the connector under Organization settings, then Connectors, using the same address and header. After that, each person opens Customize, then Connectors and selects Connect next to it.
Everyone who connects this way uses the same key, so they all see the same Mighty company. Only share it with people who should see that company's figures.
How do I know what Claude has done?
The API Keys page shows when each key was last used. Draft invoices are in your invoice list, and draft bank suggestions are on the bank transaction, ready for you to approve or change. Mileage claims Claude records are on the Mileage Claims screen.
Can I use ChatGPT or another AI assistant?
Yes. ChatGPT and Gemini sign in to Mighty instead of using a key. Read How to connect ChatGPT to Mighty or How to connect Gemini to Mighty. The technical details for other assistants are in our API documentation.
