Build AI Sales & Inventory Web App + AI Chat Assistant — Apps Script, Gemini, ChatGPT, Antigravity

A sales and inventory ERP that runs on Google Sheets, covering the full trading cycle — quotation, sales order, invoice, payment, ledger — with an AI chat assistant sitting on top of your own data. Built as an Apps Script web app, so there is no server to rent and no database to configure.

What it does

A customer asks for a price: you build a quotation with searchable customer and product pickers, apply discounts per line or across the total, and watch the document render live beside the form. Print it, email it, or mark it accepted and convert it to a sales order in one click — and only then does stock move. Confirmed orders become invoices with your tax rate applied, and every transaction posts to the customer ledger, which you can filter by date range and print. Suppliers work the same way in reverse: purchase orders, supplier ledgers and payments recorded against a balance.

Highlights

• Stock deducts on the sales order, never on the quotation — the distinction that keeps inventory honest
• Products in pieces, kilograms, litres or boxes, with plus/minus stock adjustments that record a reason
• Reports for sales, top customers, top products, inventory, receivables and profit and loss
• Tax settings for GST, service tax and sales tax, editable rather than hard-coded
• Three roles — admin, sales manager, sales staff — with an About App page documenting what each one can do
• Currency symbol, app name and logo set once and applied everywhere, including printed documents
• SWR loading: data caches locally and refreshes silently in the background instead of reloading the page

The AI chat assistant

Add your own OpenAI API key in settings, pick a model, and ask questions in plain English — "top five customers by revenue", "unpaid invoices over 30 days". It reads your sheets and answers from the real figures. The key is yours, so you control the model and the spend.

Who it is for

Distributors, wholesalers and trading businesses that quote before they sell and need stock, receivables and profit in one place. The five AI prompts used to build it are included if you want to extend it yourself.