curl --request POST \
  --url https://api.numeralhq.com/tax/customers \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "name": "Customer Name",
  "email": "customer@example.com",
  "is_tax_exempt": true,
  "reference_customer_id": "20506"
}'

{
  "id": "cus_123456789",
  "object": "tax.customer",
  "reference_customer_id": "20506",
  "name": "Customer Name",
  "email": "customer@example.com",
  "is_tax_exempt": true
}