Validate sort codes and account numbers in real time with official BACS algorithms. Catch bad details before payments fail - from 1.9p per check.
Modulus checking is an industry-standard validation method used to verify that a UK sort code and account number combination is valid before processing a payment.
Our service uses the official BACS-approved modulus checking algorithms (Modulus 10 and Modulus 11) to mathematically verify that account details are correctly formatted and could represent a valid bank account.
Invalid payment details cost UK businesses over £800 million annually in failed transactions, administrative overhead, and customer service issues.
Catch invalid account details before submission
Provide instant feedback on data entry errors
Reduce manual intervention and customer support
Uses official modulus checking algorithms
Simple integration, powerful validation
Customer inputs sort code and account number in your payment form
Your system sends a validation request to our API endpoint
Our system applies modulus checking algorithms in under 100ms
Receive immediate validation result with detailed feedback
Integrate in minutes with our developer-friendly API
curl -X GET "https://wsp.esortcode.com/uk/v1/validateaccount?key=YOUR_API_KEY&sortcode=200000&accountNumber=12345678"const apiKey = 'YOUR_API_KEY';
const sortCode = '200000';
const accountNumber = '12345678';
const url = `https://wsp.esortcode.com/uk/v1/validateaccount?key=${apiKey}&sortcode=${sortCode}&accountNumber=${accountNumber}`;
const response = await fetch(url);
const result = await response.json();import requests
api_key = 'YOUR_API_KEY'
sort_code = '200000'
account_number = '12345678'
url = f'https://wsp.esortcode.com/uk/v1/validateaccount?key={api_key}&sortcode={sort_code}&accountNumber={account_number}'
response = requests.get(url)
result = response.json()$apiKey = 'YOUR_API_KEY';
$sortCode = '200000';
$accountNumber = '12345678';
$url = "https://wsp.esortcode.com/uk/v1/validateaccount?key={$apiKey}&sortcode={$sortCode}&accountNumber={$accountNumber}";
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$result = json_decode(curl_exec($ch), true);
curl_close($ch);{
"modulusCheck": {
"sortcode": "200000",
"accountNumber": "12345678",
"valid": true
},
"branches": [
{
"bankName": "BARCLAYS BANK PLC",
"branchTitle": "Head Office",
"address1": "1 Churchill Place",
"town": "London",
"postcode": "E14 5HP",
"bacsPayments": true,
"directDebits": true,
"directCredits": true
}
]
}Pay only for what you use - annual packs from 4.0p to 2.5p, monthly from 2.4p to 1.9p
Choose annual or monthly, then drag the slider or tap a preset
50 free checks to try the API · no card required
Higher packs unlock lower per-check rates
Everything you need for production-grade validation
TLS 1.3 encryption, SOC 2 compliance
Daily database updates for accuracy
Detailed dashboards and reporting
Expert technical support team
Real-time notifications and callbacks
Validate hundreds of records at once
Mission-critical apps need enterprise-grade reliability
Financial penalties for downtime
Separate from standard service
24/7 priority support
Personal point of contact
Add to any monthly subscription · Covers Modulus Checking & CoP (our infrastructure) · EISCD not included
Start validating sort codes and account numbers in minutes
50 free checks included • No credit card required • 5-minute setup