Prepare and file overdue German VAT returns with Claude Cowork and Claude in Chrome

Posted

Feb 9, 2026 by Andrew Jefferson (@EastlondonDev)

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Last checked

Oct 16, 2026

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Method:

How we verify

Evidence: Shown on videoThe source includes a video or screen recording of the agent doing the task.

Outcome

From a folder of invoice and receipt PDFs, Claude Cowork prepared quarterly accounts; after the poster logged in to the Elster tax portal, Claude in Chrome found, filled and submitted the Q3 2025 VAT forms.

Agent

Claude Cowork, Claude in Chrome

The source didn't share its exact prompt, so we wrote this from what it describes.

Here's a task I'd like your help with. Read it all the way through before you start.

Goal: Prepare my quarterly accounts from my invoices and receipts, then fill in my VAT return on the German tax portal (Elster).

Check with me first: Which quarters do I need to file?

What I'll give you:
- A folder with PDFs of my invoices and receipts
- My Elster login (I'll log in myself)

Rules:
- First prepare the accounts for each quarter and show me the totals.
- Once I've logged in, find the right VAT forms and fill them in from those accounts.
- If something is missing or unclear, ask me instead of guessing.
- Don't submit until I've reviewed the figures and said yes.

Output: Quarterly accounts plus the filled VAT forms, ready for my final check.

You'll know it worked when: the forms match my quarterly totals and I'm comfortable pressing submit.

Works best when: I check the numbers myself before anything is filed.

Here's a task I'd like your help with. Read it all the way through before you start.

Goal: Prepare my quarterly accounts from invoices and receipts and fill in the VAT return on ELSTER for my review.

Quick check first: tell me if anything below is missing or unclear.

Inputs (fill in or confirm):
- Folder of invoice and receipt PDFs
- Quarters to file
- ELSTER login (I'll log in)
- Small-business (Kleinunternehmer) status, if any

Rules:
- First prepare a quarter summary: net, VAT rate and VAT per invoice and receipt, with file names.
- Separate output VAT (sales) and input VAT (purchases) and show the payable or refundable amount.
- Use only documents in the folder; list missing ones.
- Enter figures into the right ELSTER fields (Kennzahlen) and note which field got which number.

Checkpoint: Do not submit (übermitteln) the return; stop at the review screen for me.

If you get stuck: If ELSTER asks for the certificate file or PIN, stop and hand over. If a login, CAPTCHA or two-step code appears, stop and ask me to handle it; never guess or store passwords.

Verify before you finish: Check ELSTER's calculated total matches your summary.

Output: Quarter summaries, field mapping table and a screenshot of the review screen.

Done when: each return is filled correctly and waiting for my submission.

Source

https://x.com/EastlondonDev/status/2020826097890242582