Bank Transfer Payment Codes is a Craft Commerce gateway for plain bank transfer that prints scannable payment codes on the order confirmation, in order emails and in PDFs.

What it does

Gateway: behaves like Commerce's own Manual gateway — the order completes with a pending authorisation, and capturing it (from the CP, or through markPaid()) marks the order paid.
Four code formats: EPC QR (SEPA, GiroCode, Zahlen mit Code), HUB-3 PDF417 (Croatia), UPN QR (Slovenia), PAY by square (Slovakia), each registered through EVENT_REGISTER_FORMATS so third parties can add their own.
Seven payment reference schemes: HR00, HR01, SI12, Belgian structured communication, Finnish/Estonian reference number, Slovak variable symbol, and the ISO 11649 RF fallback for everywhere else.
_code.twig partial: one visible code, a "try another code" switcher when more than one format applies, plain-text payment details with copy buttons.
Order-email PNGs: embedded as inline CID parts by default, or served from a signed anonymous URL in hosted mode for mailers that strip attachments.
Single markPaid() API for the CP Capture button, ERPs and future bank-statement imports, with an EVENT_AFTER_MARK_PAID event.
Croatian, Slovenian, German and Slovak translations.

Setup

composer require wmd/craft-bank-transfer-payment-codes
php craft plugin/install bank-transfer-payment-codes
Commerce → System Settings → Gateways → New gateway, type Bank transfer with payment codes.
Settings → Plugins → Bank Transfer Payment Codes, add one bank account per merchant account the store can pay into (IBAN, BIC, formats, reference scheme, address).

Formats

Handle	Countries	Notes
`epc`	eurozone	EPC QR / GiroCode, EUR only, BIC required outside the EEA
`hub3`	HR	HUB-3 PDF417, Croatian IBAN, EUR
`upn`	SI	UPN QR, Slovenian IBAN, EUR
`paybysquare`	SK	PAY by square, mandatory logo frame

Full documentation: README.