Build an invoice generator app that totals itself and saves as PDF
If you send a handful of invoices a month, you don't need accounting software to make them; you need a form that adds up correctly, remembers your details and prints cleanly. Anticode can build an invoice generator app like that, running in your browser. It won't send invoices, collect payment or apply tax rules for you, and this page is clear about where those jobs go instead.
What goes on an invoice
Requirements vary by country and by whether you're registered for sales tax or VAT, so check your own tax authority's guidance. Most invoices include:
- Your business name, address and contact details, plus any registration or tax number you're required to show.
- The customer's name and address.
- A unique, sequential invoice number.
- The invoice date and, where relevant, the date the work was done or goods supplied.
- Line items: description, quantity, unit price and line total.
- Subtotal, any tax at its rate, and the total due, with the currency.
- Payment terms and how to pay: bank details or a payment link.
Features that make it quick to use
- Saved sender details
- Your name, address, logo drawn as text or a simple mark, bank details and default terms, entered once and filled in on every new invoice.
- Customer list
- Customers you've invoiced before, picked from a list so their address is filled in.
- Line items
- Add, remove and reorder lines; quantities and prices total as you type. A discount line and a tax rate field you set.
- Numbering
- The next number suggested automatically (INV-0042 after INV-0041), always editable.
- Due date
- Calculated from the terms (14 or 30 days), and shown clearly.
- Status
- Draft, sent or paid, set by you, so a list view shows what's outstanding.
- Duplicate
- Copy last month's invoice for a retainer client and change the dates.
Getting the arithmetic right
Money in JavaScript needs care: adding 0.1 and 0.2 doesn't give exactly 0.3. Ask for amounts to be calculated in whole pence or cents and only formatted as currency for display. Decide whether tax is calculated per line or on the subtotal, and round once at the point your tax authority expects. Test with awkward numbers: a quantity of 0.5, a price of 33.33, a 20% rate.
Print and PDF from the browser
The app builds the invoice as a page with a print stylesheet: an A4 or Letter layout, no buttons or menus, sensible page breaks for long item lists. You then use the browser's print dialog, where every modern browser offers "Save as PDF" as a destination. That gives you a PDF to attach to an email without the app generating files itself. Ask for a large "Print or save as PDF" button and check the result on the paper size you use.
Describing it to Anticode
"An invoice generator for a freelance photographer in the UK. Saved business details and bank details, a customer list, line items with quantity and unit price, optional VAT at a rate I set, numbering from INV-0100, 14-day terms, draft/sent/paid status and an outstanding total. A clean A4 print layout. Pounds." The model writes it as one app that runs in your browser; your details, customers and invoices are saved on that device for next time.
If you track hours, the time tracking app can feed it: ask for both in one app so a week's billable entries become invoice lines.
What it doesn't do
Anticode apps run in a sandbox with no network and no payments, which means:
- No sending. The app can't email an invoice. Save the PDF and attach it to an email yourself.
- No payment collection. It can't take a card payment. You can print a payment link from your own provider (a Stripe Payment Link, PayPal or similar) on the invoice as text for the customer to visit.
- No tax rules. It applies the rate you enter. It doesn't know VAT, GST or sales tax rules, reverse charge, or which items are exempt.
- No e-invoicing. Countries that require structured electronic invoices through a government system need dedicated software.
- No bookkeeping. Paid status is just a label you set; nothing reconciles with your bank.
- One device. Invoices live in that browser; export them regularly, and keep the PDFs as your actual records.
When you have regular clients, recurring billing or an accountant who needs your records, accounting software is the right next step.
Questions people ask
Is an invoice generator app like this legally enough for my business?
It produces whatever content you tell it to include. Whether that meets your local invoicing rules is for you or your accountant to check.
Can I add my logo?
The sandbox doesn't load images from other sites, but you can add your own logo image to the build. Or ask for your business name set in a chosen style, or a simple mark drawn in code.
Can customers pay from the invoice?
Only by following a payment link or bank details you include. The app itself can't process payments.