Mono Acquiring — monobank card payments for OpenCart 2.3, 3.x and 4.x

Mono Acquiring for OpenCart is a payment module that adds monobank acquiring card payments to your store. The module creates an invoice via the bank’s API, sends the customer to monobank’s secure payment page, and after payment accepts a webhook, checks its ECDSA signature and changes the order status itself. The admin doesn’t need to manually check who paid — statuses in OpenCart update automatically.

How mono acquiring works in OpenCart

1. At checkout, the customer chooses monobank card payment and confirms the order.
2. The module calls the monobank API, creates an invoice with a set lifetime and redirects the customer to the bank’s payment page — the card is entered on monobank’s side, not in your store.
3. The bank sends a webhook to extension/mono_acquiring/payment/mono.callback (on OpenCart 3.x and 2.3 — extension/payment/mono/callback). The module verifies the ECDSA signature (the X-Sign header) and sets the order status you chose in the settings — separately for a successful payment, a failed/expired one, and a refund.
4. With two-stage payment (Pro), funds are first held on the card and charged only once you confirm the order — handy when you need to check stock before charging.
5. Refunds (Pro) are done from the payment log in the admin: in full or for a specified amount, without logging into the bank’s dashboard.

Under the hood

• Cryptographic webhook verification: the X-Sign signature (base64 ECDSA-SHA256) is checked against the merchant’s public key — the module rejects a faked “order paid” request.
• Dedicated tables cc_mono_order and cc_mono_card — payments and card wallet tokens are stored separately and don’t touch OpenCart’s standard tables.
• A full monobank API client: creating an invoice with cart contents (basketOrder), a status request, finalise for hold payments, refunds.
• A bilingual admin — Ukrainian and English localisation out of the box.
• Auto-fiscalisation via an OpenCart event — a PRRO module subscribes to the event and issues a receipt right after successful payment.

How to install

1. Upload mono_acquiring.ocmod.zip via Extensions → Installer in the OpenCart admin. For 3.0.x take mono-oc3-1.1.4.ocmod.zip, for 2.3 take mono-oc2-1.1.3.ocmod.zip and upload the upload/ folder’s contents to the store root over SFTP.
2. In Extensions → Payments, find Mono Acquiring and click “Install” — the module will create its tables. Pro isn’t switched on by this: the trial is only issued by clicking “Try Pro” in the settings.
3. Open the settings, paste the token (test or live) and click “Test token” — you’ll see your merchant name.
4. Choose the payment type (charge immediately or hold), the order statuses, and save.
5. The module shows the webhook URL in its settings and passes it to the bank automatically when creating an invoice.
6. For Pro, after purchase paste the licence key from the email into the “Pro licence” field.