Invoicing as a Google Sheets add-on

rechnungs.tools began as a Google Sheets add-on for writing invoices.

The idea was simple: many freelancers already trust spreadsheets, so the first version used Google Sheets as the database. Invoice rows, customer data, sender profiles, and generated documents all lived close to the workflow users already understood.

Publishing a Google Sheets add-on to the Marketplace was its own product lesson. The add-on had to fit the permissions model, the review process, and the expectations of people who do not want an accounting system. They want to send a correct invoice and get back to work.

Getting a well-structured tool experience out of a spreadsheet took a lot of workarounds: macros that build user interfaces on the fly, mechanisms to lock sheets down, and still no support for things like drag and drop. The familiarity of a sheet is worth a lot, but you never get full freedom, and the user experience trade-offs kept piling up.