How to add Products with Quantities to Invoices in Airtable

When creating invoices or purchase orders, you often need to associate products or services with specific quantities. In this article, we’ll walk through how to set this up in Airtable.

We’ll start with a simple example using two tables: Invoice and Product.

• The Product table contains basic fields like id, name, variant, and unit price.

• The Invoice table initially only contains an id.

Our goal is to add multiple products with different quantities to a single invoice. We could directly add Product to the Invoices table, as linked records. While this allows us to add multiple products, it doesn't let us specify quantities for each product directly — and that’s the challenge we’ll solve.

Concept of Line Items table:

The core idea behind this approach is to treat each line item (Product + Quantity) as an individual record, which can then be associated to an invoice. This setup allows us to create multiple line items and link all of them to a single invoice. The diagram below illustrates this structure.

In the following illustration of a Purchase Order, we are mapping each line item to a table called "PO - Line Item" in Airtable.

Line Item as a Individual Record:

A single line item in an invoice or purchase order typically includes a Product, Quantity, Unit Price, and Price (calculated as Unit Price × Quantity). We’ll model this structure step by step.

Start by creating a new table called Line Items.
In this table:

• Set Id field as Primary field.

• Add Invoice as a linked record field. Disable Allow linking to multiple records in the options.

• Add Product as a linked record field and disable Allow linking to multiple records in the options.

• Add Quantity as a number field.

• To compute the total, we need the unit price — so we’ll add Unit Price as a lookup field from the Product table.

• Finally, add a Price field using a formula: Quantity * Unit Price.

Instead of having autonumbers in Id field, we can also set it as a combination of Invoice and Product, as they are unique for each line item.

• Change the Id field in Line Items table to be a formula field, with formula as {Invoice} & " - " & {Product}

Back to the Invoice Table

Now that we’ve created a model for line items, let’s complete the setup in the Invoice table.

You’ll notice that a new field for Line Items has been automatically added to the Invoice table. This happens when you link the Invoice table from within the Line Items table — Airtable creates the reverse relationship for you.

Once you start adding line items and linking them to an invoice, you’ll see those items listed in the corresponding invoice record.

All that’s left is to calculate the total price.

To do this,

• Add a Rollup field in the Invoice table. Set it to sum the Price field from the linked Line Items records.

And that's it. drum rolls…

Wrapping Up

This setup allows you to associate multiple products with different quantities and compute totals — something that isn’t possible with a simple linked field.

This flexible model lays the foundation for automating invoices, calculating totals, and generating PDF documents.

If you're looking to generate polished Invoice documents directly from Airtable, check out FlexiPage — our tool that lets you create custom templates and automatically fill them with your Airtable data.