Invoice Generator with Stock Alerts – Google Apps Script

An invoicing system that knows about your stock. Raise an invoice and the items come off inventory; delete it and they go back. That link between billing and stock is what turns an invoice generator into something a shop can actually run on.

Stock that stays correct

Every invoice deducts the items sold, and deleting an invoice restores them — so a cancelled sale does not quietly leave your stock count wrong. A low stock alert fires when an item drops past its threshold, which is the difference between reordering on time and finding out when a customer asks for something you no longer have.

The invoicing itself

• Login system with users stored in Google Sheets
• Create, update and delete invoices
• Automatic invoice number generation
• Line items added, edited and removed in real time
• Auto calculation of subtotal, tax and grand total
• Custom payment method dropdowns you define yourself
• Printable clean invoice layout

The dashboard

An invoice dashboard with filters and running totals shows what has been billed over a period rather than making you scroll a sheet. The admin panel manages the item catalogue and the payment methods behind it all.

Who it suits

Retail shops and small distributors where billing and stock are the same job, service businesses that also sell parts, and anyone who has outgrown a plain invoice template.

Setup

Copy the sheet, load your items and their stock levels, deploy the script. Google Sheets holds the invoices, items and users. The video covers the full build, and support is free if you get stuck.