Your API Key
Use this key to authenticate your requests to the Opentax API
This key is stored locally in your browser and is only visible to you
Quick Start Example
Dutch Box 1 Income Tax Calculation (2025)
cURL Request
curl -X POST https://opentax.dev/api/2025/nl/box-1 \
-H "Authorization: Bearer " \
-H "Content-Type: application/json" \
-d '{
"income": 75000,
"birthdate": "1980-01-01"
}'