Verify UK National Insurance Number (NINO) structure
Verify UK National Insurance Number (NINO) structure, validate HMRC prefix rules, detect administrative/temporary numbers, map historical quarter returns, and calculate DWP benefit signing day
Request
- x-api-key: <your-api-key>
- Content-Type: application/json
Response
{
"isValid": true,
"ninoDetails": {
"benefitPaymentDay": "8",
"formattedPrint": "PL61 1090 1014 0000 0712 1981 2874",
"historicalQuarter": "<historical quarter>",
"normalized": "PL61109010140000071219812874",
"prefix": "<prefix>",
"rawInput": "PL61109010140000071219812874",
"sequenceNumber": "<sequence number>",
"suffix": "<suffix>"
},
"status": "success",
"tokensDeducted": 1,
"validationResult": {
"isAdministrativeNumber": true,
"isFormatValid": true,
"isPrefixValid": true,
"isSuffixValid": true,
"reason": "checksum ok"
}
}What it does
Verify UK National Insurance Number (NINO) structure, validate HMRC prefix rules, detect administrative/temporary numbers, map historical quarter returns, and calculate DWP benefit signing day
Request
Body
| Field | Type | Required | Description |
|---|---|---|---|
nino | string | yes | UK National Insurance Number string (e.g., "QQ 12 34 56 C" or "AB123456C") |
Example request
{
"nino": "QQ123456C"
}Response
| Field | Type | Description |
|---|---|---|
isValid | boolean | |
ninoDetails | object | |
↳ benefitPaymentDay | string | |
↳ formattedPrint | string | |
↳ historicalQuarter | string | |
↳ normalized | string | |
↳ prefix | string | |
↳ rawInput | string | |
↳ sequenceNumber | string | |
↳ suffix | string | |
status | string | |
tokensDeducted | integer | |
validationResult | object | |
↳ isAdministrativeNumber | boolean | |
↳ isFormatValid | boolean | |
↳ isPrefixValid | boolean | |
↳ isSuffixValid | boolean | |
↳ reason | string |
Example response
{
"isValid": true,
"ninoDetails": {
"benefitPaymentDay": "8",
"formattedPrint": "PL61 1090 1014 0000 0712 1981 2874",
"historicalQuarter": "<historical quarter>",
"normalized": "PL61109010140000071219812874",
"prefix": "<prefix>",
"rawInput": "PL61109010140000071219812874",
"sequenceNumber": "<sequence number>",
"suffix": "<suffix>"
},
"status": "success",
"tokensDeducted": 1,
"validationResult": {
"isAdministrativeNumber": true,
"isFormatValid": true,
"isPrefixValid": true,
"isSuffixValid": 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/nino' \
-H 'x-api-key: <your-api-key>' \
-H 'Content-Type: application/json' \
-d '{"nino": "QQ123456C"}'const res = await fetch('https://app.castomapi.com/v1/verify/nino', {
method: 'POST',
headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
body: JSON.stringify({"nino": "QQ123456C"})
});
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/nino', {
method: 'POST',
headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
body: JSON.stringify({"nino": "QQ123456C"})
});
const data = await res.json();
console.log(data);import requests
res = requests.post(
'https://app.castomapi.com/v1/verify/nino',
headers={'x-api-key': '<your-api-key>'},
json={"nino": "QQ123456C"},
timeout=30,
)
print(res.json())<?php
$ch = curl_init('https://app.castomapi.com/v1/verify/nino');
curl_setopt_array($ch, [
CURLOPT_CUSTOMREQUEST => 'POST',
CURLOPT_RETURNTRANSFER => true,
CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
CURLOPT_POSTFIELDS => json_encode(['nino' => 'QQ123456C']),
]);
$data = json_decode(curl_exec($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 UK National Insurance Number (NINO) structure 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