Automated monthly invoicing

A month of invoicing: from one hour to thirteen seconds.

Sector : Media — A French-language radio group

The context

At the end of every month, a full month of work had to be invoiced by hand. Open the calendar, find each engagement, apply the right rate depending on whether it fell on a weekday or a weekend, account for multi-day engagements, travel and administrative fees, then copy it all into a spreadsheet and write the invoice.

The problem

An hour of repetitive work, every month, on pricing rules you know by heart but can still misapply on a tired evening. And a pricing mistake only surfaces when the client spots it.

What was built

The calendar is read automatically. Each engagement is priced by the real rules — weekday or weekend, duration, travel, fees. The result is written to the tracking spreadsheet, the invoice goes out as HTML by email, and a comparison table projects the current month against the previous one.

What it changes

A full month of invoicing runs in thirteen seconds, from calendar to sent email. No more re-entry: the pricing rules are written once and applied identically every month.

How it works

An n8n workflow triggered at the start of the month. The agenda is read through the Google Calendar API, rates are computed in a code node — that is where the business rules live, not in a language model — results are written to Google Sheets through the API, then the invoice HTML is generated and sent over SMTP. The current-month projection is computed in the same pass and attached to the email.

What this could look like for you

Any business that invoices per engagement is concerned: a practice billing hours, a tradesperson billing jobs, an agency billing interventions. The principle is the same — your pricing rules already exist, they simply live in your head rather than in a machine. The work is writing them down, once.