Claude connector for German bookkeeping: claude.ai in the browser and on your phone

What you need before you start

• A Claude account. According to Claude's help center (checked 30 October 2026), custom connectors are available on the Free, Pro, Max, Team and Enterprise plans; a Free account can hold one custom connector.
• A company at jahresabschluss.io that uses the bookkeeping, the EÜR (cash-basis accounts) or the tax module. Only such companies are offered on the consent page.
• The Administrator or Preparer role in that company's workspace, plus your second factor — approving the connection creates a key for the company, and creating keys needs both.
• Nothing to install and nothing to copy. The connector signs in with your jahresabschluss.io account instead of a pasted key.

Add the connector in claude.ai

Claude's help center (checked 30 October 2026) describes the route for individual plans like this. Menu names change from time to time; if your screen differs, follow the current help article:

Where:    Customize › Connectors › + Add › Add custom connector
Name:     Buchhaltung   (the name in your connector list)
URL:      https://jahresabschluss.io/mcp
Sign-in:  OAuth — no API key, no request headers
Client:   Register automatically   (if Claude asks)
Then:     Add, and Connect if shown — jahresabschluss.io opens

If you are not yet signed in at jahresabschluss.io in that browser, you sign in first, with your password and, where you set one up, your second factor. Claude's help center lists three ways for Claude to identify itself to a server (the “OAuth client” setting): Claude's published identity, “Register automatically” and your own OAuth client. Our server supports automatic registration, so if Claude shows that choice, pick “Register automatically” — you never type a client ID or a secret.

Type the address exactly. Claude's help center points out that custom connectors are not checked by the provider of Claude, so the address you enter is the server you trust with your books.

The consent page, field by field

This page at jahresabschluss.io decides what Claude can do. Claude asks; you choose.

Click “Allow”, confirm with your second factor if you are asked for it, and you are back in Claude. “Reject” connects nothing. The short note at the bottom of the page sums up the rules: the access applies to this one company only, the program never files with the tax office itself, and you can revoke it at any time under “AI agent & API”.

What each right unlocks in Claude

Claude only sees the tools your rights allow; the others do not appear in its tool list.

• Read: get_saldenliste (the trial balance), list_journal_entries, list_open_items, list_bank_transactions, list_receipts, get_vat_return, list_tax_deadlines, get_annual_report and the other lookups.
• Post: confirm_receipt, create_receipt_upload_link and get_receipt_inbox_address (for getting original receipts into the books), book_bank_transaction, match_bank_transaction, create_outgoing_invoice, create_journal_entry and storno_journal_entry — and, for VAT returns, check_tax_filing, prepare_tax_filing and request_tax_filing_approval.
• Send invoices by e-mail: send_outgoing_invoice, to stored addresses only.
• Not on the consent page: locking periods (Festschreibung, the GoBD period lock) and webhooks. Lock months in the app, or give the desktop extension or Claude Code a key you create yourself under “AI agent & API” with the right to lock periods. Webhooks are set up through the REST interface, not through Claude.

A first conversation

With Read and Post ticked, a first session might look like this — all figures are an example:

You:     Which customer invoices are overdue, and what do we owe
         in VAT for September 2026?

Claude asks to use the connector  → you allow
Claude → list_open_items          overdue receivables
       → get_vat_return           period 2026-09

Claude:  Three invoices are overdue, € 7,140 in total; the oldest
         is 58 days late. Advance VAT for September: € 1,265.40
         payable (box 83). Shall I look at the receipts waiting?

You:     Yes. Book the clear ones and ask me about the rest.

Claude → list_receipts, get_receipt_proposal
       → confirm_receipt          one by one, after your OK

Claude's help center advises choosing “Allow always” only for servers and tools you trust to run unsupervised. For bookkeeping, a sensible habit is to let lookups run and to approve each posting yourself. Independently of that, our server instructs Claude to get your explicit yes before it issues or emails an invoice, reverses an invoice or deletes a receipt — and that yes covers that one step only.

On your phone

There is nothing to set up twice. Claude's help center says that a connector you connect on the web or in Claude Desktop is available in Claude for iOS and Android the next time you sign in there; adding connectors directly on mobile is described as a beta. For every Claude client, the requests to our server come from the cloud of Claude's provider, not from your phone.

On the phone, short questions work well: “Has the payment from the agency arrived?”, “What is still unbooked this week?”. For a VAT return, Claude can prepare everything and hand you the approval link; filing then happens in the jahresabschluss.io app, signed in, with your ELSTER PIN.

Receipt photos are the one thing not to drop into the chat: an attachment reaches Claude as an image, never our server as a file, and our server tells Claude not to book from what it read. Ask for an upload link instead — Claude creates one with create_receipt_upload_link, valid for 30 minutes, for up to 20 files, no sign-in. Open it on the phone, choose the photo or PDF, then tell Claude it is there; it shows you the proposal and books after your yes.

Team and Enterprise plans

On Claude's Team and Enterprise plans an owner adds the connector once under Organization settings › Connectors, and each member then connects individually (per Claude's help center). With our address every member goes through the consent page in person: their own sign-in, their own company, their own rights and validity — and each connection becomes a key of its own.

Claude's help center warns that a fixed credential stored in a shared connector gives everyone the same access. Signing in per person avoids exactly that: you can see each colleague's connection in “AI agent & API” and revoke it on its own.

Expiry, reconnecting and revoking

• No silent renewal: when the validity you chose runs out, Claude's calls are refused and you connect again.
• Connecting again replaces your previous connection from the same program to the same company; the old key is revoked.
• Every connection appears in your key list under “AI agent & API”, named after the program and its destination (claude.ai).
• Removing the connector in Claude ends it on Claude's side. To end it on our side too, revoke the key under “AI agent & API”.

Limits: what stays with you

• Claude never files with the tax office. It runs the official ELSTER check without sending anything and prepares the filing; you file in the app with your PIN.
• The bank connection, company settings and business partners' IBAN/BIC are managed in the app only.
• The annual financial statements (Jahresabschluss) are prepared, reviewed and issued in the app; afterwards Claude can read the issued version with get_annual_report.
• What Claude reads is processed by the provider of Claude under your Claude account's terms.
• Claude's answers and postings are proposals you accept. Responsibility for the books stays with the company and its managing directors.

Frequently asked questions

Which Claude plans can add the jahresabschluss.io connector?

Per Claude's help center (checked 30 October 2026): Free, Pro, Max, Team and Enterprise. A Free account can hold one custom connector; on Team and Enterprise an owner adds it and members then connect individually.

Do I have to paste an API key into Claude?

No. You sign in at jahresabschluss.io and approve. The key for the chosen company is created in the background and never appears in the chat.

Does the connector work in the Claude app on my phone?

Yes. Once connected on the web or in Claude Desktop, it is available in Claude for iOS and Android at your next sign-in there, according to Claude's help center.

Can Claude file my VAT return through the connector?

No. With the Post right Claude checks and prepares the return and gives you an approval link. You file in the app with your ELSTER PIN, which never goes into the chat.

What happens when the connection expires?

Claude's calls are refused. Connect again from Claude's connector settings and approve once more; the previous connection is replaced.

Can one connection cover two companies?

No. Each approval covers exactly one company. To work on another one, connect again and choose it on the consent page.