If you don't have one, start a Google Sheet with columns: Invoice number, Client, Client email, Amount, Due date, Paid (Yes/No). Mark paid ones as you get paid.
In ChatGPT, go to Settings, then Apps, and connect Gmail (and Google Drive if your sheet is there). Read what each permission allows.
Open a new chat (not inside a Project, because tasks in Projects can't read Project files) and paste the 'Monday overdue check' prompt below, filled in.
ChatGPT shows a confirmation with the schedule. Check it says every Monday at your time and in your time zone. You can edit it later under Scheduled.
In Settings, then Notifications, choose push or email so you're told when the list is ready.
On Monday, read the list, open each draft in Gmail, fix anything (a client may have paid another way) and send it yourself.
Add a line to the task: for invoices over 30 days late, draft a firmer second reminder for you to review.
Every Monday at [8:00am], [time zone]: 1. Open my invoice list [Google Sheet name] (or search my Gmail sent mail for invoices from the last 90 days). 2. Find every invoice where Paid is not 'Yes' and the due date is before today. 3. Give me a list: invoice number, client, amount in [currency], days overdue, total overdue. 4. For each one, create a Gmail draft (do NOT send) to the client: subject 'Friendly reminder: invoice [number]', under 90 words, polite, with the amount, due date, how to pay ([bank transfer details / payment link]) and 'please ignore this if you've already paid'. Sign it [your name, business]. 5. If a client has replied about this invoice in the last 14 days, don't draft a reminder; tell me instead. Never send, mark as paid or change my sheet. Only read and draft.
From https://usecasy.com/use-case/chatgpt-overdue-invoice-reminders/ · Guide checked 23 October 2026 · Prices are rough and shown in USD unless stated (MYR where relevant).