FlatInvoice for Shopify.
FlatInvoice creates PDF invoices, packing slips, receipts, and credit notes for every order in your Shopify store (the platform many online stores run on) automatically — with your logo, a tax ID line, and sequential numbering, and no theme code to edit.
What FlatInvoice does.
- Unlimited PDF invoices, packing slips, receipts, and credit notes created automatically for every order.
- Every invoice is emailed to the customer automatically the moment they order — on by default, and you can turn it off or switch it to send when the order ships instead.
- Add a VAT/GST tax ID line and get gap-free sequential invoice numbers (INV-0001, INV-0002…) on every document.
- Pick your brand colour straight from your logo in one click.
- Every new order gets its invoice automatically; any order from the last 60 days can also be invoiced in one click, no bulk import needed.
Who FlatInvoice is for.
Store owners who need to hand a customer or a B2B buyer a real invoice or packing slip without editing Liquid templates or building one by hand. If you only need an occasional basic printable receipt, Shopify's own free Order Printer app may be enough; FlatInvoice is for stores where an invoice goes out on every order.
How FlatInvoice works.
Install & start your trial
Install from the Shopify App Store. Billing is handled by Shopify, and nothing is charged during the trial.
Set up your invoice
Enter your business details and tax ID, and pick an accent colour from your logo in one click.
Invoices send themselves
Every new order gets a numbered PDF invoice automatically, emailed to the customer unless you turn that off.
Questions people actually ask.
Does FlatInvoice support VAT or GST?
Yes — add your VAT/GST registration number and choose a tax label, and both appear on every PDF alongside gap-free sequential invoice numbers. It does not do PEPPOL e-invoicing; if your business needs that EU standard, a dedicated e-invoicing app is the better fit.
Can it email invoices to customers automatically?
Yes — this is on by default for a new install. Every customer gets their PDF invoice by email when the order is placed; you can switch that to send on fulfillment instead, or turn it off.
Is there a free plan?
No. FlatInvoice has one plan with a free trial. Shopify's own Order Printer app is free but basic and usually needs template edits to look professional.
Does it work with orders I already have?
Every new order gets invoiced automatically. For orders already on your store, FlatInvoice can generate an invoice or packing slip in one click for anything from the last 60 days.
Is FlatInvoice legit, and who builds it?
It is a publicly listed Shopify app, reviewed and published by Shopify at apps.shopify.com/flatinvoice, developer Stelar Digital LLC, a registered US company in Roseville, California. Billing runs through Shopify, so you cancel from your Shopify admin.