"PAY by square" is a national standard for QR code payments that was adopted by the Slovak Banking Association in 2013. It is incorporated into a variety of invoices, reminders and other payment regulations.
It's simple, I couldn't find any implementation of "PAY by square" standard for JavaScript, so I decided to create one and share it with the community to help individuals and businesses to create QR codes for their invoices.
- TypeScript support
- Compatible with Slovak banking apps
- Isomorphic Browser & Runtime-independent implementation
Note
Since v3, the implementation is considered stable and specification-complete. No breaking changes are planned. Only minor improvements and bug fixes may be introduced.
$ npm install bysquare<script type="module">
import { encode, decode } from "https://esm.sh/bysquare@latest";
</script>This library provides encode and decode functions to work with the data
model directly, allowing you to create customized payment solutions.
This example shows how to generate a payment QR code and display it in a web page:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>Payment QR Code</title>
</head>
<body>
<div id="qrcode" style="width: 200px"></div>
<script type="module">
import { QRCode } from "https://esm.sh/@lostinbrittany/qr-esm@latest";
import { encode, PaymentOptions, CurrencyCode } from "https://esm.sh/bysquare@latest";
const qrstring = encode({
payments: [
{
type: PaymentOptions.PaymentOrder,
amount: 123.45,
variableSymbol: "987654",
currencyCode: CurrencyCode.EUR,
bankAccounts: [
{ iban: "SK9611000000002918599669" }
],
},
],
});
const qrElement = document.getElementById("qrcode");
qrElement.appendChild(QRCode.generateSVG(qrstring));
</script>
</body>
</html>To generate QR codes for different payment types, use the encode function with
the appropriate payment configuration:
import {
CurrencyCode,
encode,
PaymentOptions,
Periodicity,
} from "bysquare";
// Simple Payment (Payment Order)
const qrstring = encode({
payments: [
{
type: PaymentOptions.PaymentOrder, // 1
amount: 50.75,
variableSymbol: "123456",
currencyCode: CurrencyCode.EUR, // "EUR"
bankAccounts: [
{ iban: "SK9611000000002918599669" },
],
},
],
});
// Standing Order
const qrstring = encode({
payments: [
{
type: PaymentOptions.StandingOrder, // 3
amount: 100.0,
variableSymbol: "654321",
currencyCode: CurrencyCode.EUR, // "EUR"
day: 15,
month: Month.January, // Single month
periodicity: Periodicity.Monthly, // "m"
bankAccounts: [
{ iban: "SK9611000000002918599669" },
],
},
],
});
// Direct Debit
const qrstring = encode({
payments: [
{
type: PaymentOptions.DirectDebit, // 2
amount: 25.0,
variableSymbol: "789012",
currencyCode: CurrencyCode.EUR, // "EUR"
bankAccounts: [
{ iban: "SK9611000000002918599669" },
],
},
],
});For standing orders that should execute in specific months, you can combine multiple months using bitwise OR operators:
import {
CurrencyCode,
encode,
encodeOptions,
Month,
PaymentOptions,
Periodicity,
} from "bysquare";
const qrstring = encode({
payments: [
{
type: PaymentOptions.StandingOrder,
amount: 100.0,
variableSymbol: "654321",
currencyCode: CurrencyCode.EUR,
day: 15,
// Execute in January, July, and October only
month: Month.January | Month.July | Month.October, // Results in 577
periodicity: Periodicity.Monthly,
lastDate: "20251231",
bankAccounts: [
{ iban: "SK9611000000002918599669" },
],
},
],
});
// Alternative: Use the utility function to encode multiple months
const monthsToEncode = [Month.January, Month.July, Month.October];
const encodedMonths = encodeOptions(monthsToEncode);
const qrstring2 = encode({
payments: [
{
type: PaymentOptions.StandingOrder,
amount: 100.0,
variableSymbol: "654321",
currencyCode: CurrencyCode.EUR,
day: 15,
month: encodedMonths, // Same result: 577
periodicity: Periodicity.Monthly,
lastDate: "20251231",
bankAccounts: [
{ iban: "SK9611000000002918599669" },
],
},
],
});Note
Date Format: Provide date inputs (e.g., paymentDueDate, lastDate)
in ISO 8601 format (YYYY-MM-DD). They are automatically converted to
YYYYMMDD during encoding to match the Pay by Square specification.
For more complex data with multiple payments and additional fields:
Note
Encoded data are without diacritics
The library removes all diacritics from the input data to ensure maximum
compatibility, as not all banks support diacritics, which may lead to errors.
If you need to retain diacritics, disable deburr option when encoding data -
encode(model, { deburr: false }).
import {
CurrencyCode,
DataModel,
decode,
encode,
PaymentOptions,
} from "bysquare";
const data = {
invoiceId: "random-id",
payments: [
{
type: PaymentOptions.PaymentOrder,
currencyCode: CurrencyCode.EUR,
amount: 100.0,
variableSymbol: "123",
paymentNote: "hello world",
bankAccounts: [
{ iban: "SK9611000000002918599669" },
// ...more bank accounts
],
// ...more fields
},
// ...more payments
],
} satisfies DataModel;
// Encode data to a QR string
const qrstring = encode(data);
// Decode QR string back to the original data model
const model = decode(qrstring);The library provides utility functions for working with multiple classifier options as specified in the PAY by Square standard. These functions are particularly useful for handling multiple month selections in standing orders.
import {
encodeOptions,
Month,
} from "bysquare";
// Encode multiple months into a single value
const monthsArray = [Month.January, Month.July, Month.October];
const encoded = encodeOptions(monthsArray);
console.log(encoded); // 577 (1 + 64 + 512)
// This matches the specification example:
// January=1, July=64, October=512, sum=577$ npm install --global bysquareEncode JSON or JSONL data from files and print the corresponding QR code.
$ bysquare --encode file1.json file2.json...
$ bysquare --encode file.jsonlDecode the specified QR code string and print the corresponding JSON data. The qrstring argument should be a valid QR code string.
$ bysquare --decode <qrstring>
This library uses permissive validation to ensure maximum compatibility with various Slovak banking applications. The validation does not strictly enforce all XSD schema restrictions.
| Aspect | Behavior |
|---|---|
| IBAN | Validated (format + checksum via ISO 13616) |
| BIC | Validated (format via ISO 9362) |
| Currency | Validated (ISO 4217, case-insensitive, includes XXX) |
| Date | Validated (ISO 8601 format) |
| Symbols | Permissive (accepts letters, spaces - XSD pattern not enforced) |
| Amounts | Permissive (accepts negative values) |
| Field lengths | Not enforced |
For reference, the official XSD schema defines these constraints (not enforced by this library):
| Field | Max Length | Pattern |
|---|---|---|
variableSymbol |
10 | [0-9]{0,10} |
constantSymbol |
4 | [0-9]{0,4} |
specificSymbol |
10 | [0-9]{0,10} |
paymentNote |
140 | - |
originatorsReferenceInformation |
35 | - |
invoiceId |
10 | - |
beneficiary.name |
70 | - |
beneficiary.street |
70 | - |
beneficiary.city |
70 | - |
mandateId |
35 | - |
creditorId |
35 | - |
contractId |
35 | - |
amount |
15 | >= 0 |
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