Square Invoice & Subscription Builder from Text (GPT-4o Mini)

Turn plain text invoice requests into Square invoices (and subscriptions) automatically

The Square Invoice & Subscription Builder from Text (GPT-4o Mini) sub-workflow takes invoice details written in plain language, uses OpenAI (GPT-4o-mini) to normalize them, then calls the Square API to find or create the customer, create and publish an email-delivered invoice, and—when requested—set up a monthly subscription.

What this workflow does

Designed for n8n workflow chains, this sub-workflow receives invoice fields from a parent workflow via an Execute Workflow trigger and performs these steps:

• Accepts invoice fields: name, email, item, amount, notes, recurring flag (e.g., Monthly), and date.
• Uses OpenAI structured output (GPT-4o-mini) to clean and normalize the invoice data, including converting the date to YYYY-MM-DD and generating a unique invoice number.
• Finds or creates a Square customer by searching customers using the email address.
• Checks customer profile to determine whether the customer has a card on file.
• Creates a Square order, then creates and publishes a Square invoice configured for email delivery.
• Optionally creates a monthly subscription: if the invoice is marked as Monthly, it creates a Square subscription plan and plan variation and attaches it to the customer.
• Returns results: if not recurring, it returns the published invoice public URL to the parent workflow.

Use cases

• Generate Square invoices from support tickets or intake forms that contain invoice details in free text.
• Create subscription invoices for “monthly” customers without manual Square setup.
• Enable SaaS operators to streamline billing handoffs from an n8n front-end workflow.

Technical details

• OpenAI: n8n nodes including n8nn8n-nodes-langchainagent and chat model nodes using GPT-4o-mini with a structured output parser.
• Square API: uses HTTP requests with Square access token authorization and your Square location ID to create customers, orders, invoices, and subscriptions.
• Logic nodes: if, set, and supporting workflow elements for routing recurring vs. one-time invoices.