AI & automationHow-to
ChatGPT and Claude bookkeeping: connect your Nefin books
Nefin Team5 min read
If Claude or ChatGPT is already open on your screen all day, that's where bookkeeping questions come up: who still owes us for September, what did we spend on software this year, can you invoice the studio for last week. Nefin's AI connector lets that chat reach your books directly, so the answer comes from your ledger instead of a guess, and a request like "invoice them" becomes a real draft in Nefin.
- In an AI app connected to Nefin, someone asks for an invoice to Lumen Studio: 12 hours of design at 75.00 plus 20% VAT, due in 30 days.
- The AI app finds the client in Nefin, then asks before creating anything, and the change is allowed.
- A draft invoice INV-1043 appears in Nefin: 900.00 plus VAT 180.00, total 1,080.00, due 11 Nov 2026, and the audit log marks it as made via MCP.
- The AI app replies with a summary: it's a draft, and nothing posts until it is activated.
- Back in Nefin, the invoice is checked and marked as sent, which posts it to the ledger.
What you can ask for
- "Who owes us money, and how late are they?" It reads your customers' balances or runs the aging report.
- "Show me profit and loss for the last quarter." Profit and loss, balance sheet, cash flow and more come straight from Nefin's reports.
- "Invoice Lumen Studio for 12 hours of design at 75.00 plus VAT, due in 30 days." It finds the client and creates a draft invoice, numbered by Nefin.
- "Here's last month's bank statement. Import the lines and book the obvious ones." On plans with bank reconciliation, it imports the lines, then books the ones you agree with as payments, fees or transfers.
- "Attach this receipt to the bill from Nordic Office Supplies." The file goes onto the bill, next to the entry.
Before you start
- A Nefin account on any plan. Connectors are included from Starter up.
- AI switched on for the company. It's on by default; an owner or admin can turn it off, or back on, in Settings, Company.
- Two-step verification on your Nefin login. If you haven't set it up, Nefin walks you through it the first time you connect.
In Nefin, open Settings, AI connectors. It shows the server URL with a copy button (the same address works in every AI app) and step-by-step tabs for Claude, ChatGPT, Gemini, Claude Code, Cursor and VS Code.
Connect Claude
- In Claude on the web, desktop or phone, open Customize, Connectors and click Add custom connector. On a Team or Enterprise plan, an owner adds it for everyone first.
- Name it Nefin and paste the server URL.
- For sign-in, choose Register automatically, or leave the OAuth client ID and secret empty. Don't pick Use Claude's published identity; Nefin doesn't support it yet. Click Add.
- Click Connect next to Nefin, sign in with your two-step code, check the companies it will reach, and click Allow access.
Connect ChatGPT
- In ChatGPT on the web, open your settings and switch on Developer mode.
- In the apps and connectors settings, click + to create an app for a remote MCP server. Name it Nefin and paste the server URL.
- For authentication choose OAuth and leave the client ID and secret empty. Save the app.
- Click Connect next to Nefin, sign in with your two-step code, check the companies and click Allow access.
Read-only, or allowed to make changes
The sign-in screen has an Allow changes box, and it starts unticked. Leave it off and the connection can only read. Tick it and the AI app can also create and change records. The connector has 29 tools in all:
| Kind | What the tools do | Read-only connection |
|---|---|---|
| Read (13 tools) | Reports, contacts, invoices and bills, journals, payments, bank lines and reconciliation, payroll | Yes |
| Draft | Add contacts, accounts, items and VAT rates; create draft invoices and bills; import statement lines; set a salary; attach files | No |
| Change the books | Activate an invoice or bill, record payments, post journal entries, book statement lines, run payroll, delete drafts | No |
Tools that change the books are flagged as such, so AI apps that ask before risky actions ask you first. In Claude you can set each Nefin tool to always allow, needs approval or blocked.
What it can't do
- More than you can. Every call runs as you, with your role's permissions in that company. If your role can't post journals, neither can the AI app, and the company's IP allowlist still applies.
- Send anything to your clients. Activating an invoice posts it, but nothing is emailed. Sending stays with you, in Nefin.
- Delete what's already in the books. It can delete only draft or void invoices and bills, and only for an owner or admin.
- Pick a company on its own. If you belong to several, each request has to name one, and the AI app is told to ask you rather than guess.
When something is refused, the message says why and who can fix it, such as reconnecting with Allow changes ticked, or asking an owner or admin to turn AI on in Settings, Company. The AI app is told to pass it on rather than guess another cause.
Keeping track
Every change an AI app makes is in the audit log under your name, marked "via MCP" with the app's name, and you can filter the log to show only AI connector changes. Under Account, AI connectors you'll find every connected app and personal token; disconnect one and it stops working on its next call. Personal tokens, for tools that can't sign in with a browser, expire after 30, 90 or 365 days and are shown only once.
Limits
Each company gets 5,000 tool calls a month on Starter, 20,000 on Professional and 50,000 on Business. Reads count as well as writes. At the limit, calls pause until the 1st of the next month; nothing is charged on top. Each person can make up to 60 requests a minute, which only a runaway loop will reach.
What lands in your books
A draft invoice or bill posts nothing. It sits in Nefin's lists like one you started yourself, until you, or the AI app with your approval, activate it. From there it's an ordinary document: same journal, same reports, same audit trail.
