Create an invoice, share a secure link, get paid — that's the entire workflow, no client portals or account registrations required. Invio distills billing into its absolute minimum viable surface while still producing legally compliant EU electronic invoices in Factur-X/ZUGFeRD 2.2 BASIC, UBL 2.1, and Italian FatturaPA formats, all embedded as XML attachments inside WeasyPrint-rendered PDFs. The Deno 2 backend uses Hono v4 for HTTP routing with SQLite persistence, while the SvelteKit 2 frontend styled with Tailwind CSS v4 and DaisyUI v5 delivers a responsive interface that stays out of your way. The team access system includes a permission matrix, TOTP-based two-factor authentication, and OIDC integration with configurable auto-provisioning — drop it into existing identity infrastructure without manual user management. Preset products let you build invoices from reusable catalog items. A change history log tracks every modification for audit purposes. Rate limiting protects the API behind reverse proxies. The entire stack ships as a single multi-stage Docker image containing Deno, Bun, Node, WeasyPrint, and all required font packages — zero external service dependencies beyond the container itself. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Unlicense licensed.