How much does modulus checking cost?

Modulus checking starts from 1.9p per check on monthly volume (2.4p at 10,000 checks/month). Annual packs are 2.5p at 100,000 checks. Enterprise SLA customers get additional discounts and priority support.

What algorithms does eSortcode use?

eSortcode uses all BACS-approved modulus checking algorithms including Modulus 10, Modulus 11, Double Alternate, and exception handling for special cases. Our algorithms are regularly updated to match BACS Standard 18 requirements.

BACS-approved · From 1.9p

UK sort code and account validation

Q: What is modulus checking?

Modulus checking validates UK bank account numbers using mathematical algorithms (Mod 10, Mod 11, Double Alternate) to detect errors and prevent payments to invalid accounts. It's required by UK payment schemes including BACS, Faster Payments, and CHAPS.

Official modulus algorithms. Catch bad details before the payment fails.

View pricing Try a check

Mod 10, Mod 11, Double Alternate · typically under 50ms · 50 free test checks

Modulus check Example

Sort code: 09-01-28
Account: 12345678
Result: Valid
Bank: Santander UK plc
Time: 14 ms

{ "valid": true, "algorithm": "MOD11" }

Overview

What is Modulus Checking?

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.

Did you know?

Invalid payment details cost UK businesses over £800 million annually in failed transactions, administrative overhead, and customer service issues.

Key Benefits

Reduce Failed Payments
Catch invalid account details before submission
Improve User Experience
Provide instant feedback on data entry errors
Lower Operational Costs
Reduce manual intervention and customer support
BACS Compliant
Uses official modulus checking algorithms

Process

How it works

Simple integration, powerful validation

Details entered

Sort code and account number in the payment form.

API call

Your system sends a validation request.

Check

Modulus algorithms run, typically under 50ms.

Result

Valid or not, with bank details when the number checks.

Simple RESTful API

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);

Response

{
  "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
    }
  ]
}

Pricing

Transparent modulus pricing

Pay only for what you use - annual packs from 4.0p to 2.5p, monthly from 2.4p to 1.9p

Estimate your modulus cost

Choose annual or monthly, then drag the slider or tap a preset

Checks per year Volume pricing · min 500

500 checks

500 50k 100k

Price per check
4.00p
volume rate

Pack total

£20.00

+ VAT · one-time

You save: £0.00 vs 4.0p baseline

Credits valid for a minimum of 12 months

No setup fees or minimum commitments

Get started

50 free checks to try the API · no card required

Volume tiers at a glance

Higher packs unlock lower per-check rates

500 checks

4.0p

£20.00

Baseline

1,000 checks

3.8p

£38.00

5% off

5,000 checks

3.4p

£170.00

15% off

10,000 checks

3.2p

£320.00

20% off

25,000 checks

2.9p

£725.00

27.5% off

50,000 checks

2.7p

£1,350.00

32.5% off

100,000 checks

2.5p

£2,500.00

37.5% off

100,000+ checks

10,000 checks/month

2.4p

£240

£2,880

20,000 checks/month

2.3p

£460

£5,520/year

30,000 checks/month

2.25p

£675

£8,100/year

40,000 checks/month

2.2p

£880

£10,560/year

50,000 checks/month

2.1p

£1,050

£12,600/year

60,000 checks/month

2.05p

£1,230

£14,760/year

70,000 checks/month

2.0p

£1,400

£16,800/year

80,000 checks/month

1.95p

£1,560

£18,720/year

90,000 checks/month

1.92p

£1,728

£20,736/year

100,000 checks/month

1.9p

£1,900

£22,800/year

100,000+ checks/month

Enterprise Features Included

Everything you need for production-grade validation

Bank-Grade Security

TLS 1.3 encryption, ISO 27001 certified

Real-time Updates

Daily database updates for accuracy

Usage Analytics

Detailed dashboards and reporting

24/7 Support

Expert technical support team

Webhook Support

Real-time notifications and callbacks

Batch Processing

Validate hundreds of records at once