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One POST away from cleared.

A pragmatic REST API, signed webhooks, a sandbox that talks to a real APP, and SDKs for the three runtimes you actually use. Read the docs in an afternoon. Ship in a sprint.

curl -X POST https://api.involums.com/v1/invoices \
  -H "Authorization: Bearer sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
    "buyer": { "tin": "14829034-0001" },
    "items": [{
      "name": "Consulting — May 2026",
      "quantity": 1,
      "unit_price": 485000,
      "tax_category": "VAT_STANDARD"
    }]
  }'

# → 200 OK · Cleared by NRS in 7.2s
# → "irn": "A7F3-9201-4D6E-..."

A sandbox that talks to a real APP

Submit invoices, simulate clearance and rejection codes, fire webhooks — without consuming your live quota.

Sandbox guide →

Webhooks with signed payloads

Subscribe to invoice.cleared, invoice.rejected, certificate.expiring. We sign every payload with HMAC-SHA256 and retry up to 5 days.

Webhook reference →

OpenAPI 3.1, generated SDKs

Node, Python, and PHP SDKs auto-built from the spec. Generate your own client for Go, Ruby, or Rust — the schema is yours.

Download spec →

Official SDKs

Node.js
1.4.2
npm install @involums/sdk
Python
1.2.0
pip install involums
PHP
0.9.0 (beta)
composer require involums/sdk