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
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"
}
}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
| Field | Type | Required | Description |
|---|---|---|---|
businessName | string | no | Optional business or legal entity name for audit context |
permitNumber | string | yes | The sales tax resale permit or exemption ID string to verify |
stateCode | string | yes | Two-letter US state ISO code (e.g., "CA", "TX", "NY", "FL") |
Example request
{
"businessName": "Ada Lovelace",
"permitNumber": "<permit number>",
"stateCode": "ABC-123"
}Response
| Field | Type | Description |
|---|---|---|
isValid | boolean | |
permitDetails | object | |
↳ expectedFormatExample | string | |
↳ normalized | string | |
↳ officialVerificationPortal | string | |
↳ permitType | enum | One of: SALES_TAX_PERMIT, RESALE_CERTIFICATE, EXEMPT_ORGANIZATION, DIRECT_PAY_PERMIT, UNKNOWN. |
↳ rawInput | string | |
↳ stateCode | string | |
↳ stateName | string | |
↳ taxAuthority | string | |
status | string | |
tokensDeducted | integer | |
validationResult | object | |
↳ hasNoSalesTax | boolean | |
↳ isFormatValid | boolean | |
↳ isStateSupported | boolean | |
↳ reason | string |
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.
400 | The body or a parameter failed validation. The details array names the field. |
401 | No key, a revoked key or a wrong header. Send x-api-key. |
402 | The wallet cannot cover this call. Top up or wait for the monthly grant. |
404 | The resource does not exist, or it is not yours. Both answer identically and cost nothing. |
429 | Over the per-minute quota of your tier. Back off and retry. |
5xx | Upstream 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 key | 10 |
| Free | 60 |
| Pro | 300 |
| Enterprise | 1200 |
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