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POST /v1/verify/sales-tax-exemption free No key needed Verify

Verify US State Sales Tax Resale Permits

Verify US State Sales Tax Resale Permits, Seller Numbers, and Tax Exemption IDs against state-specific syntax rules and tax department specifications

POST

Request

  • x-api-key: <your-api-key>
  • Content-Type: application/json

Response

{
  "isValid": true,
  "permitDetails": {
    "expectedFormatExample": "<expected format example>",
    "normalized": "PL61109010140000071219812874",
    "officialVerificationPortal": "<official verification portal>",
    "permitType": "SALES_TAX_PERMIT",
    "rawInput": "PL61109010140000071219812874",
    "stateCode": "ABC-123",
    "stateName": "Ada Lovelace",
    "taxAuthority": "3.74"
  },
  "status": "success",
  "tokensDeducted": 1,
  "validationResult": {
    "hasNoSalesTax": true,
    "isFormatValid": true,
    "isStateSupported": true,
    "reason": "checksum ok"
  }
}
The response below is a mock built from the endpoint's own schema — no request leaves this page. Edit the body, press Send, read the shape you will get back. Run it for real in the dashboard →

What it does

Verify US State Sales Tax Resale Permits, Seller Numbers, and Tax Exemption IDs against state-specific syntax rules and tax department specifications

Request

Body

FieldTypeRequiredDescription
businessNamestringnoOptional business or legal entity name for audit context
permitNumberstringyesThe sales tax resale permit or exemption ID string to verify
stateCodestringyesTwo-letter US state ISO code (e.g., "CA", "TX", "NY", "FL")

Example request

{
  "businessName": "Ada Lovelace",
  "permitNumber": "<permit number>",
  "stateCode": "ABC-123"
}

Response

FieldTypeDescription
isValidboolean
permitDetailsobject
  ↳ expectedFormatExamplestring
  ↳ normalizedstring
  ↳ officialVerificationPortalstring
  ↳ permitTypeenumOne of: SALES_TAX_PERMIT, RESALE_CERTIFICATE, EXEMPT_ORGANIZATION, DIRECT_PAY_PERMIT, UNKNOWN.
  ↳ rawInputstring
  ↳ stateCodestring
  ↳ stateNamestring
  ↳ taxAuthoritystring
statusstring
tokensDeductedinteger
validationResultobject
  ↳ hasNoSalesTaxboolean
  ↳ isFormatValidboolean
  ↳ isStateSupportedboolean
  ↳ reasonstring

Example response

{
  "isValid": true,
  "permitDetails": {
    "expectedFormatExample": "<expected format example>",
    "normalized": "PL61109010140000071219812874",
    "officialVerificationPortal": "<official verification portal>",
    "permitType": "SALES_TAX_PERMIT",
    "rawInput": "PL61109010140000071219812874",
    "stateCode": "ABC-123",
    "stateName": "Ada Lovelace",
    "taxAuthority": "3.74"
  },
  "status": "success",
  "tokensDeducted": 1,
  "validationResult": {
    "hasNoSalesTax": true,
    "isFormatValid": true,
    "isStateSupported": true,
    "reason": "checksum ok"
  }
}

Errors

Every error answers with the same envelope: an HTTP status, a machine code and a sentence.

400The body or a parameter failed validation. The details array names the field.
401No key, a revoked key or a wrong header. Send x-api-key.
402The wallet cannot cover this call. Top up or wait for the monthly grant.
404The resource does not exist, or it is not yours. Both answer identically and cost nothing.
429Over the per-minute quota of your tier. Back off and retry.
5xxUpstream refused or timed out. The call is not billed.

Code

curl -X POST 'https://app.castomapi.com/v1/verify/sales-tax-exemption' \
  -H 'x-api-key: <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{"businessName": "Ada Lovelace", "permitNumber": "<permit number>", "stateCode": "ABC-123"}'
const res = await fetch('https://app.castomapi.com/v1/verify/sales-tax-exemption', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"businessName": "Ada Lovelace", "permitNumber": "<permit number>", "stateCode": "ABC-123"})
});
const data = await res.json();
console.log(data);
import { request } from 'node:https';

// Node 18+ has fetch built in
const res = await fetch('https://app.castomapi.com/v1/verify/sales-tax-exemption', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"businessName": "Ada Lovelace", "permitNumber": "<permit number>", "stateCode": "ABC-123"})
});
const data = await res.json();
console.log(data);
import requests

res = requests.post(
    'https://app.castomapi.com/v1/verify/sales-tax-exemption',
    headers={'x-api-key': '<your-api-key>'},
    json={"businessName": "Ada Lovelace", "permitNumber": "<permit number>", "stateCode": "ABC-123"},
    timeout=30,
)
print(res.json())
<?php
$ch = curl_init('https://app.castomapi.com/v1/verify/sales-tax-exemption');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
    CURLOPT_POSTFIELDS => json_encode(['businessName' => 'Ada Lovelace', 'permitNumber' => '<permit number>', 'stateCode' => 'ABC-123']),
]);
$data = json_decode(curl_exec($ch), true);
print_r($data);

Cost and limits

This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.

Rate limits per minute

No key10
Free60
Pro300
Enterprise1200

Docs → Pricing

Questions

What does Verify US State Sales Tax Resale Permits cost?

This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.

How do I authenticate?

Send your key in the x-api-key header. One key covers every metered endpoint; there is nothing to enable per endpoint.

Can I send an Authorization: Bearer token instead?

Not for a metered endpoint — those take the x-api-key header and nothing else. Bearer tokens belong to the account side: the dashboard and account APIs accept a JWT session, and castomapi-auth issues those through a standard OAuth2 handshake, with authorization code, client credentials and refresh grants. The auth service page covers it.

What are the limits?

10 requests a minute per IP with no key at all, 60 a minute on the free tier, 300 on Pro, 1200 on Enterprise. Above the no-key tier the quota is per account, across every endpoint.

OpenAPI: https://app.castomapi.com/docs/json