Invoice 14

Invoice 14 is our own product: a free online invoicing system for freelancers and small service businesses. It grew out of the invoicing we do for our own clients and is now available to anyone on a free plan—up to fourteen invoices a year, no credit card required—with paid plans for higher volumes, quotes, VERI*FACTU submission, and team workspaces.

Compliance first: drafts stay flexible, but an issued invoice becomes a record. Issuing locks the invoice with the next sequential number in its series, snapshots every amount, and makes it immutable—later changes go through voiding or corrective invoices, never edits. Totals are calculated with multi-rate IVA and Spanish IRPF withholding, intra-EU customers get VIES-validated reverse-charge treatment with the right legal wording, and on paid plans each issued invoice is submitted to the AEAT through a fiscal provider, printing the tax QR and the VERI*FACTU legend on the PDF.

Built for more than one country: tax names, rate presets, and tax-ID formats follow where the business is registered—Spain, the UK, France, Germany, Italy, Portugal, the Netherlands, Ireland, and the US out of the box, with editable rates for forty-plus more. The app itself is bilingual (English and Spanish), and every customer carries an invoice language, so PDFs and emails render in English, Spanish, German, Italian, or French to match the recipient.

From draft to paid: invoices are emailed as polished PDFs with one click, payments are recorded against them, and the dashboard shows what is outstanding, overdue, and billed by quarter. Quotes convert into invoices, a product catalogue with per-customer negotiated prices speeds up repeat billing, and the whole workspace can be exported as JSON at any time.

Tech stack: TanStack Start (React) for the app and its server functions, Clerk for authentication and workspace memberships, PostgreSQL with Drizzle for append-only invoice records and serialised numbering, @react-pdf/renderer for the PDFs, Resend for email delivery, Tailwind for the UI, PostHog and Sentry for analytics and error tracking, and DigitalOcean App Platform with Doppler-managed configuration for hosting.