Features
SlimFact is the invoicing platform that does the heavy lifting. From creating an invoice to getting paid — everything you need in one clean package.
📄 Invoices, Bills & Receipts
One system, three document types. Create professional invoices, send bills, and issue receipts. Each flows naturally into the next:
- Bill → paid → Receipt → Invoice — convert as the transaction progresses
- Immutable once opened — your records stay clean and auditable
- Tax rates per line, inclusive or exclusive — handle any tax scenario
- Decimal quantities and per-mille support — precision where it matters
- Due dates, payment terms, and automatic status tracking
💳 Online Payments
Your customers pay online. You get notified. No manual reconciliation.
- iDEAL / Wero — the most popular Dutch online payment method
- Credit cards — Visa, Mastercard, and more
- Multi-PSP routing — route iDEAL through Mollie and credit cards through Stripe, or mix and match
- Down payments — require partial payment upfront
- Cash & bank transfer — for offline payments with transaction tracking
- Automatic status sync — webhooks update invoice status when payment completes
- Refunds — process refunds directly through your PSP
🔄 Subscription Billing
Set it and forget it. Recurring invoices run on cron schedules while you focus on your business.
- Cron-based scheduling — every Monday, first of the month, quarterly, whatever you need
- Start and end dates — subscriptions that run for a fixed period
- Active/inactive toggle — pause subscriptions without deleting them
- Each subscription generates proper numbered invoices automatically
👤 Client Portal
Your customers get their own space. They see what they owe, when it's due, and can pay right there.
- Personal dashboard with all invoices, bills, and receipts
- Pay online directly from the invoice page
- Real-time status updates — pending, open, paid
- No account creation needed — share the invoice link and they're in
🏢 Companies & Clients
Run multiple businesses from one account. Each company gets its own identity.
- Company profiles — name, address, banking details, VAT ID, CoC number, logo
- Company-specific prefixes — keep invoice numbers separate per company
- Client records — contact person, address, email, VAT ID
- Number prefix templates —
{year}-{num},INV-{company}-{num}, whatever you need - Configurable starting numbers — pick up where your old system left off
📧 Email & Communication
Send invoices by email. Know when they're read.
- Customizable email templates — Handlebars-powered with per-locale variants
- Open tracking — a URL query parameter tells you when a customer clicks the invoice link from their email
- Per-company email settings — different sender addresses and BCC per company
- Send, resend, reply — full email workflow from the invoice detail view
🎨 Typst Invoice Rendering
SlimFact uses Typst — a modern, open-source typesetting engine — to render invoices. Unlike traditional HTML-to-PDF converters, Typst produces crisp, perfectly aligned layouts with professional-grade typography.
- SVG preview — invoices render instantly in the browser as scalable SVG, with zero layout shifts
- PDF export — one-click download as a print-ready PDF with embedded fonts
- Multi-language templates — English, Dutch, and German invoice templates with localized field names, date formats, and payment instructions
- Customizable templates — invoice layouts are written in Typst, a clean, readable markup language. You can add your own templates for custom branding, different document types, or industry-specific layouts
- Company branding — logo, address, banking details, and CoC/VAT numbers rendered inline
- Flexible layouts — A4 and US Letter page sizes, inclusive/exclusive tax display, automatic multiline descriptions
- Invoice type awareness — automatically shows the correct title (Invoice, Bill, Receipt, or Concept) based on document status
- EPC QR codes — scannable payment QR codes embedded directly in the PDF for instant bank transfers
📦 Exports & Formats
- PDF — download from the public invoice page
- Digiboox — format for Digiboox integration (Settings → Exports)
- EPC QR codes — scannable payment codes on every PDF invoice
- UBL XML — attached automatically to sent OPEN/PAID invoice emails
🔌 Headless API
SlimFact is API-first. Every feature available in the UI is also available through the API.
- tRPC — type-safe RPC with automatic client generation
- OIDC authentication — works headless with any OIDC provider
- Webhook callbacks — get notified of payment events
- Build custom frontends, integrate with your ERP, or automate your entire billing workflow
🔐 Authentication & Security
Your data stays yours. Authentication is handled by your existing identity provider.
- OpenID Connect — federated SSO with any OIDC provider
- Multiple roles — administrator, point of sale, and customer
- No separate user database — your IdP is the source of truth
📱 Technical Excellence
- Fully responsive — works on desktop, tablet, and mobile
- Database-backed — all invoices stored in PostgreSQL for advanced querying
- On-the-fly PDF generation — no stale files, always the latest template
- Multi-language — English, Dutch, and German UI
- Self-hosted — runs on your own infrastructure with Docker Compose
- ~160 req/s — handles over 14 million API calls per day on modest hardware
