Integration · Accounting

Connect Claude & ChatGPT to Quaderno

Ask your AI which Quaderno invoices are still outstanding, what tax applies to a sale, or whether a customer's VAT number is valid. It can create contacts, invoices, estimates, credit notes and expenses, record payments and email invoices to customers. Tax and invoicing questions get answered without opening Quaderno.

Connect Quaderno free

Free plan, no credit card. Takes about a minute.

Try asking

“Which invoices are late or still outstanding?”
The AI searches invoices by state and lists the unpaid ones with contact, date and total.
“What tax applies if I sell a digital product to a customer in Germany?”
It calculates the sales tax, VAT or GST for that country and product type and shows the rate and amount.
“Is the VAT number DE123456789 valid?”
It checks the tax ID for the given country and tells you whether it is valid.

What your AI can do

Invoices and estimates

Search, create and update invoices and estimates, convert estimates to invoices, record payments and email invoices.

Tax checks

Calculate the sales tax, VAT or GST for a sale and validate a customer's tax ID.

Contacts, credits and expenses

Manage contacts, issue and send credit notes, record expenses and read receipts, recurring invoices and products.

“Invoice Acme Ltd for 3 hours of consulting at 120 EUR.”
It finds the contact, creates the invoice with one line and lets Quaderno calculate the tax. Nothing is emailed until you ask it to send the invoice.
“Record that invoice 1045 was paid by bank transfer today.”
It records the payment on the invoice with amount, date and payment method. No money is moved.
“Turn estimate 88 into an invoice.”
It converts the accepted estimate into a real invoice and shows you the new invoice.

29 tools for Quaderno

These tools are switched on when you connect. You can switch any of them off, or require your approval before it runs.

calculate_taxCalculate the sales tax, VAT or GST that applies to a sale, given the customer's `to_country` and optionally postal code, city, tax ID, product type and amount.
convert_estimate_to_invoiceVisible to othersTurn an accepted estimate into a real invoice by `proforma_id`. The new invoice is a legal tax document.
create_contactChanges dataCreate a customer or vendor contact. `first_name` is required (the company name for a company contact); add email, address, country and tax ID as needed. Search first to avoid duplicates.
create_credit_noteChanges dataIssue a credit note (refund document) against an invoice by `invoice_id`, optionally for a partial `credited_amount`. This is a legal tax document and cannot be edited afterwards.
create_estimateChanges dataCreate an estimate (proforma) for a `contact` with line `items`. It is not sent until you email it.
create_expenseChanges dataRecord an expense from a vendor `contact` with line `items`, issue date and currency.
create_invoiceChanges dataCreate an invoice for a `contact` with line `items` (description, quantity, unit price). Quaderno calculates the tax. The invoice is not emailed until you send it.
get_contactGet one contact by `contact_id`, including name, email, address, tax ID and language.
get_credit_noteGet one credit note by `credit_id`, with lines, totals and the invoice it refunds.
get_estimateGet one estimate (proforma) by `proforma_id`, with lines, totals and status.
get_expenseGet one expense by `expense_id`, with vendor, lines and totals.
get_invoiceGet one invoice by `invoice_id`, with line items, taxes, totals, payment status and PDF link.
get_productGet one product by `product_id`, with code, price, tax class and stock.
get_receiptGet one sales receipt by `receipt_id`, with lines, taxes and totals.
get_recurring_invoiceGet one recurring invoice schedule by `recurring_id`, with frequency, dates and line items.
record_invoice_paymentChanges dataRecord a payment received against an invoice by `invoice_id`, with amount, date and payment method. This only records the payment; no money is moved.
search_contactsSearch customers and vendors by name, email or other text in `q`. Use this to find a contact's ID before creating invoices or other documents.
search_credit_notesSearch credit notes by text in `q`, `state` or `date` range.
search_estimatesSearch estimates (proformas) by text in `q`, `contact`, `state` or `date` range.
search_expensesSearch expenses (purchase invoices) by text in `q`, `contact`, `state` or `date` range.
search_invoicesSearch invoices by text in `q`, `contact`, `state` (e.g. outstanding, paid, late) or `date` range. Use to find unpaid or recent invoices.
search_productsSearch your product and service catalog by text in `q`.
search_receiptsSearch sales receipts by text in `q`, `contact` or `date` range.
search_recurring_invoicesSearch recurring invoice schedules by text in `q`, `contact`, `state` or `date`.
send_credit_noteEmail a credit note to its customer by `credit_id`. This sends a real email to the customer.
send_invoiceEmail an invoice to its customer by `invoice_id`. This sends a real email to the customer.
update_contactChanges dataUpdate a contact's details by `contact_id` (first_name must be passed again), such as email, address, country or tax ID.
update_invoiceChanges dataUpdate an invoice's notes, tags, attachment, payment details or custom metadata by `invoice_id`. Amounts and lines cannot be changed here.
validate_tax_idCheck whether a customer's VAT or tax number is valid, given `country` and `tax_id`.

Set up in three steps

1
Pick the app
Create a free PipMCP account and choose Quaderno from the app list.
2
Paste your key
Enter three things: your Quaderno account name (the "acme" in acme.quadernoapp.com), your private API key from quadernoapp.com/users/api-keys, and leave the password field empty.
3
Add the link to your AI
You get a personal MCP link. Add it to Claude, ChatGPT or Cursor:
1. Click your name, then Settings › Connectors › Add custom connector.
2. Paste your link as the Remote MCP server URL.
3. Switch it on from the + menu in a chat.

Questions

What can the AI do in Quaderno?

The AI can search and read contacts, invoices, credit notes, receipts, estimates, expenses, recurring invoices and products. It can create and update contacts and invoices, create estimates, credit notes and expenses, record invoice payments, convert estimates to invoices, email invoices and credit notes, calculate tax and validate tax IDs.

Does the AI see my Quaderno API key?

No. Your Quaderno credentials are encrypted at rest and never shown to the AI. After you save them, they are not shown again, not even to you. The AI only sees the results of the tools it calls.

Can I control what the AI is allowed to do?

Yes. You choose which tools are switched on, so you can start with lookups and tax checks only. Tools that email customers, like send_invoice, can stay off until you want them, and converting an estimate into an invoice can require your approval before it runs. Every tool call is logged.

Does it work with ChatGPT?

Yes. In ChatGPT go to Settings › Apps & Connectors › Advanced and turn on Developer mode, then add your PipMCP link. Developer mode needs a paid ChatGPT plan: Plus, Pro, Business or Enterprise. The same link also works in Claude (Settings › Connectors › Add custom connector), Cursor and other MCP clients.

What does it cost?

PipMCP has a free plan with no credit card required. Paid plans bill per completed task. You also need your own Quaderno account.

Why is the password field left empty?

Quaderno uses your private API key as the username and no password. So you paste the API key, leave the password empty and add your account name, which tells PipMCP which Quaderno account to call.