How to build an invoice and quote builder with Lovable

Rule of thumb: if you send a handful of invoices a month and want to be paid by card tonight, rent one, and Wave or Zoho Invoice will do it for nothing but the card fee or their logo on your PDF. If invoicing is part of a product you sell, if your quotes carry revisions and your PDFs carry your brand, or if you bill in several currencies and do not want them converted for you, the software is worth owning, because the caps above are exactly where a growing business pays and your clients’ names and amounts are yours to keep in a database you control. The honest middle case is a business that needs to be paid online. Build this and connect a payment rail, and read the block on choosing how you get paid, because that fee exists whether you rent the software or own it.

* On this template the free-tier line to watch is the pause, not storage. The only file is a logo and the rows are small, but a free project is paused after a week without activity, and a business that invoices at month end leaves it idle for three. Pro, from $25/mo, ends the pause and keeps a daily backup for 7 days, which matters more here than anywhere else in the catalogue, because an invoice is a record you may be required to keep.

Prices and rates from supabase.com, developex.com and docs.lovable.dev, checked September 2026.

Only the first three are needed to start, and none of it touches your computer. From here, you describe what you want and Lovable builds it in the browser.

1. 01

   Set the ground rules, connect Supabase, and add sign-in with the tables

   Nothing in this app is public, so the account and the ownership rule come before any screen. Send the rules in the first message and let Lovable design the tables around them.

   PromptSet the rules, connect the backend, design the tablesCopy

   Before we build anything else, note the ground rules for this project: it is an invoicing and quoting app, the vocabulary throughout is clients, quotes, invoices, line items, templates and tax rates, every row belongs to the signed-in account and the database enforces that rather than the screen, money is stored as numbers in each document’s own currency and never converted, and any AI key lives in a server-side function. Now connect this project to Supabase and add sign-up with a full name and company name, login, logout and a profile per account. Then design the tables. Clients with name, email, phone, billing and shipping address, tax ID, account number, contact person and notes. Quotes with a number, a status of Draft, Finalized or Archived enforced by a database check and defaulting to Draft, the client’s details, quote and valid-until dates, a tax rate, a discount that is an amount or a percentage, shipping, a currency code, notes, terms and a link to the invoice it became. Invoices with the same shape plus a due date, payment terms in days, payment instructions and bank details. Line items for each with description, quantity, unit price and a per-line discount. Tax rates, templates with a settings JSON, settings as key and value JSON, and custom fields scoped to quotes, invoices or both with a values table each. Turn on row-level security so each account reaches only its own rows, with explicit checks on insert and update, line items included through the parent document’s owner.

   Say the ownership rule in the first message. Left unsaid, an assistant will reasonably filter by user in the screen, and then one forgotten filter shows another company’s invoices.

2. 02

   Get the quote editor adding up in the preview

   The hard centre. Lines that add up as you type, a discount that is an amount or a percentage, tax, shipping and a currency from a list, with a client picked from file.

   PromptBuild the clients screen and the quote editorCopy

   Build the clients screen with a searchable list and add and edit dialogs for every client field. Then build the quote editor: pick a client to fill their details or type them in, add line items with description, quantity, unit price and an optional per-line discount, and show the subtotal, a document discount as a fixed amount or a percentage, a tax rate from my tax rates, an optional shipping line and the total, recalculating as I type. Let me choose the document’s currency from a list of about thirty common ones and format every amount with the browser’s own number formatting for that currency, converting nothing. Add a quote date, a valid-until date, notes and terms, then a quotes list with search, a status filter and a sort, with the quote number as the address of its detail page.

   Try a percentage discount, a tax rate and shipping on one quote in a currency with no decimals, in the preview. If the total is off by a cent, send a follow-up about rounding before building anything on top.

3. 03

   Turn a quote into an invoice, and give both a lifecycle

   Converting without retyping, revisions of a quote, sequential numbers and the three statuses. No sent and no paid, because nothing here sends or takes money.

   PromptAdd conversion, revisions, numbering and statusesCopy

   Add a Convert to invoice action on a finalized quote that creates an invoice with the same client, lines, discount, tax, shipping and currency, numbers it INV-1, INV-2 and so on, links the two documents both ways and opens the invoice editor with a due date and payment terms in days added. Add a Duplicate action on a quote that creates a revision numbered from the original (R becomes R/1, then R/2) and make the routes handle a number with a slash in it. Then the statuses Draft, Finalized and Archived on both documents, changed from the detail page, with the database refusing any other value. Build the invoices list and editor to match the quote screens.

4. 04

   Bookmark, then ask for the PDF designs and the branding

   What the client receives. A handful of PDF designs generated in the browser with your logo and colours on all of them and a live preview. Bookmark first, because this is the screen you will iterate on most.

   PromptBuild the PDF designs and brandingCopy

   Bookmark the current version first. Then generate the PDF in the browser with a PDF library and build a template gallery with a handful of designs (professional, classic, a ledger style and a couple more), each rendering the document’s header, addresses, line items, totals, notes and terms in its currency. Add branding settings: a logo uploaded to a storage bucket limited to 5 MB and image types, primary and accent colours, a font choice and header and footer text, applied to every design with a live preview. Add a print-ready preview page per document with a Download PDF button.

   Expect several follow-up messages on the designs. Select the element in the preview to point at what should move rather than describing where it sits.

5. 05

   Add the AI template analyzer, with a log and a ceiling

   The one AI feature: a design rebuilt from an invoice you already use. It reads the layout and not the amounts, and every call is capped from the first one.

   PromptAdd the AI analyzerCopy

   Add a server-side function called analyze-template that requires a signed-in user, accepts an uploaded image or PDF of an existing invoice, sends it to the AI provider and asks the model, through a forced structured tool call, for a layout specification only: colours, typography, header layout, address sections, line-item columns, how totals are shown, footer and decorative elements. It must not read amounts or line items. Before contacting the provider, write a row to an ai_calls table and check the caller’s calls today against a limit read from settings, returning a friendly message when it is hit. Save the specification as a custom template in the gallery, rendered by the same preview and PDF code as the built-in designs.

   Say that it extracts a layout and not the contents. A model asked to read amounts off a scan will do so confidently and wrongly.

6. 06
   Destination

   Add the dashboard, reports and settings, try it as a second account, and publish

   The screens around the documents, then a second account in the preview, a downloaded PDF, and publish from the same tab.

   PromptAdd dashboard, reports, settings, demo, and publishCopy

   Build a dashboard with counts and totals by status and the most recent documents, a reports page with cards for Draft, Finalized and Archived, a sortable table of every document with CSV and PDF export, an activity page listing recent changes to quotes, invoices and clients, and a settings page for the company profile, branding, tax rates, custom fields, numbering and the default currency. Add a demo account seeded on sign-in and wiped on sign-out behind a Try the demo button I can remove before launch. Then walk me through the whole thing in the preview: sign up a second account and confirm it sees no documents, create a quote in a currency with no decimals, convert it, download the PDF and check the totals match, hit the analyzer limit on purpose and read what the app says. When it holds up, publish it.

Review the access rules (row-level security policies) on every table. For each one, tell me in simple terms who can view, add, edit, and delete records, confirm that people can only reach their own data while the right roles can reach more, and flag anything left open that shouldn’t be.

One rule outranks everything above it: the database service key and the AI provider key stay on the server, and neither one ever goes into the app a browser downloads or into a repository. Should either leak, assume it has been used, look at what your provider says was spent with it, and issue a new one the same day.

One button, and the app you have been previewing is live.

A percentage has no size until you multiply it by your own month, so do that first. Twenty invoices of $500 paid by card in a month, $10,000 in all, costs roughly $336 through Stripe (the card fee, the 30 cents on each, and the 0.4% for the invoice), about the same through Square on the free plan, and roughly $309 through PayPal at its card rate. Bank details printed on the PDF cost nothing and arrive when the client gets round to it. Whichever you pick, the paid status and the reconciliation are yours to build, because the template has neither.

Open the analyze-template function. Make the model name a setting I can change without a deploy, and set it to a current model on my provider’s price list that accepts images and structured tool calls. Add an ai_calls table that records every model call (which account, which task, which model, tokens in and out, a cost estimate, success or failure) and write to it from the function, successful or not. Then add a ceiling: a limit per account per day and a total across the whole app, both settings I can change without a deploy, checked before the function contacts the provider and returning a friendly “you have reached today’s limit” rather than an error. Do not let the browser send the limit or the cost. Then add a small usage panel to settings showing calls and estimated spend this month.

Add a “Draft from description” box at the top of the quote editor. It sends my description and my last twenty finalized quotes’ line items to the ai function and gets back suggested lines with a description, quantity and unit price each, drawn from prices I have used before where they match. Fill the editor with the suggestions marked as drafts for me to edit or delete, never save anything until I do, and keep the totals recalculating as I change them.

Add an “Overdue” filter to the invoices list for finalized invoices past their due date, and a “Draft reminder” action on each that sends the client’s name, the invoice number, the amount, the currency, the due date and how many days late it is to the ai function and gets back a short, polite reminder in my company’s voice, with a firmer version for anything more than thirty days late. Show it in a box I can edit and copy, and record in the activity feed that a reminder was drafted, since this app does not send email.

Add a second function called read-invoice that requires a signed-in account, accepts an uploaded image, PDF or CSV of an invoice or a price list, sends it to the ai function and asks for the line items (description, quantity, unit price), the currency, the tax rate and the client details it can find, each with a confidence. Show the result as a prefilled draft quote or invoice with every figure the model was unsure about highlighted for me to confirm, and never save until I do. Log it and count it against the same ceiling as the analyzer.

Add a “Summarize this month” button on the reports page that gathers the documents finalized in the selected period, grouped by currency with no conversion between them, and asks the ai function for a short summary: what was invoiced, what was quoted and not yet invoiced, the largest clients by amount, and anything unusual compared with the previous period. Show it in a box I can edit and copy, and make clear which currency each figure is in.

You bring no key and pick no provider: Lovable manages an API key per project, and if you do not name a model it chooses one from what you describe. Match the model to the job: fast and cheap for anything that runs on every record, stronger only where the reasoning matters. Send every feature above through that one integration.