Invoice Ninja is an invoicing app with the classic feature list: clients, quotes, invoices, recurring invoices, payments, expenses, a client portal. It is open source, you can host it yourself or pay for the hosted version, and it has an API that covers nearly everything the interface does. That last part is why it is on this list instead of a prettier competitor.

How I use it

My monthly invoices are mostly the same every month with different numbers. So the numbers come from a small script: it reads what was done, builds the line items, creates the invoice through the API as a draft, and I look at it before it goes out. Thirty seconds of checking replaced twenty minutes of typing, and the typing is where the mistakes used to live. Sending, reminders and the client's payment page are Invoice Ninja's job after that.

The client portal is quietly useful. A client who asks for last quarter's invoices gets a link and finds them, instead of me searching my sent mail.

What surprised me is how complete it is for the price. Recurring invoices, partial payments, credits, multiple currencies, tax rates per line. The free tier up to five clients is not a crippled demo; a freelancer with a handful of clients could run on it for years.

What annoys me: the interface. There are many settings and they are all on screen at once; the first week you click around looking for the thing you know exists. Customising the PDF beyond colours and logo means editing templates, which is a project. And email delivery is only as good as the mail setup you connect, so a wrong SPF record means invoices in spam folders and a confused client.

Who it is for

Freelancers, small agencies and anyone who invoices on a schedule and likes the idea of automating the boring half. If you need country-specific accounting integration, a local tool like Lexoffice fits better. If you send three invoices a year, a template in your word processor is fine. If you send the same twelve every month, this will give you your evenings back.

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