Card processing and gateway fees quietly erode margin on every transaction, and many merchants want to pass those costs to customers where it is legally permitted. Out of the box, Odoo has no concept of a payment-method surcharge: the payment.provider and payment.transaction models charge the cart total as-is, and while you can bolt a manual fee line onto a sale order or invoice, there is no automation that reads which provider the customer selected, computes a fee against the right tax treatment, respects local caps, and shows it transparently before the customer commits to pay. Doing this by hand is error-prone and impossible to enforce consistently across the website shop, backend sales, and POS.

This module adds a first-class surcharge engine to Odoo. We introduce a configuration model (extending res.config.settings plus a dedicated payment.surcharge.rule model) where you define, per payment.provider, a fixed amount, a percentage, or a blended rule. A @api.depends-driven compute recalculates the fee whenever the order total or selected provider changes, then writes a dedicated surcharge line onto the sale.order / account.move using a configurable service product so the amount flows correctly into amount_tax and amount_total. The fee line carries the tax position you choose (taxable, tax-inclusive, or tax-exempt), so VAT/GST is handled honestly rather than being buried. Rules support country and currency scoping via res.country, minimum-order thresholds, and hard caps so the surcharge never exceeds a legal ceiling or a fixed maximum.

Transparency and compliance are built in. On the website checkout (QWeb/OWL templates on the payment step) the fee is disclosed with its own labeled line and a short explanation before the customer confirms — never a hidden charge added after the fact. Access is governed by ir.model.access.csv and record rules so only authorized roles edit surcharge rules, and every rule change is chatter-logged. Refunds are handled safely: when an order is refunded or partially refunded via account.move reversal, the surcharge line is reversed proportionally rather than being silently retained, and credit notes reflect the correct net. The same rule engine is exposed to the XML-RPC/JSON-RPC API so external channels and marketplace integrations compute identical fees, and an optional automated action can flag orders where a manual discount would push the effective surcharge above your configured cap.

Because this is build-to-order, ECOSIRE tailors the rules, tax handling, and checkout wording to your jurisdiction and gateways rather than shipping a generic download. After a short scoping call we confirm the exact provider matrix, legal caps, and tax treatment, then build and test the module against your Odoo 17.0, 18.0, or 19.0 (Community or Enterprise) on a staging database. Typical delivery is one working week from confirmed scope. You receive the installable source, documentation, a training session, and a post-go-live support window — no fabricated demos, just working code installed on your instance.