Build an invoice app with PDFs and automatic email

From a draft to a paid invoice

Billing follows the same path every time: write the invoice, send it, record what comes in, and thank the client when it is paid. Kreova builds that path as one app, and each step uses what the step before it saved.

1. Write the invoice

Pick the client and add lines from your list of services, or type your own. Each line has a quantity, a unit price and its own tax rate, and the subtotal, tax and total are worked out from the lines. The due date follows the client's payment terms.

2. The PDF comes from the same records

The PDF is made from what the app has saved at the moment you download or send it: your studio's details from Settings, the client, the lines, the tax, the total, what has been paid and the balance due. Change a line on a draft and the next PDF shows it.

3. Mark it sent, and the email goes out with the PDF

Marking an invoice as sent locks it and sends one email to the client's billing contact, with the invoice PDF attached. Nothing is emailed while it is a draft. This is what our test produced when staff marked invoice INV-2026-021 as sent:

4. Record payments, and the balance follows

Record each payment as it arrives, with its date, method and a reference. A part payment changes the status to part paid and leaves the balance owed. The payment that brings the balance to zero marks the invoice paid and sends the client a thank-you email with a receipt PDF. In our test, a $1,000.00 deposit sent nothing, and the final $1,978.38 sent the receipt once.

5. See what you are owed

The dashboard shows the total outstanding, every overdue invoice with how many days late it is, what was paid this month, and how many invoices are at each status.

What "sent" means, and what happens when an email fails

• An email counts as sent when the mail server accepts it. It does not tell you the client received it or opened it.
• If the mail server refuses it or cannot be reached, Kreova tries again 4 more times over about an hour, then marks it failed. Each attempt and its reason is listed in Kreova, in the notification history under Services.
• Each email goes out once for each change that triggers it: marking an invoice sent, or the payment that settles it. Saving the invoice again does not send it again.
• In the rare case a server stops in the middle of a send, the client can get the same email twice. Kreova prefers a second copy to a missing invoice.
• To email your clients, connect your own email account in Services, so invoices come from your address. Until then, Kreova's shared sender only emails people on your own team, which is how we tested this example.

Who can do what

Every person signs in with their own account, and the rules are kept on the server, so hiding a button is never the only protection. As staff we tried to void a sent invoice and to change the studio's settings: the server refused both. A signed-in stranger got no invoices, clients or payments, and could not download a PDF.

Want your clients to sign in and see their own invoices? Ask for a client portal, and test it the same way.

The prompt this app was built from

Change the names, services and steps to match how you bill, then send it. Kreova asks when something important is missing.

Kreova asked a few questions first, then built it in five rounds of one to five minutes each: the first build, a "continue" request, and three requests for the invoice pages, the emails, and the clients, settings and staff pages. That used five build credits.