Cash-on-Delivery Fee / Prepayment Discount for OpenCart 2.3, 3.x and 4.x

Cash on delivery costs a store money: the carrier’s fee, return shipping for refused parcels, tied-up cash and a percentage of unclaimed orders. COD Fee / Prepayment Discount lets you shift that difference into the checkout: the chosen payment method adds a separate line to the order total — a surcharge or a discount. The customer sees it before confirming the order, and the amount recalculates every time they switch payment method.

How it works, step by step

1. You create a rule: choose a payment method (for example “Cash on delivery”), a mode — surcharge or discount — and an amount type — fixed or a percentage of the base.
2. Set the limits. For a percentage, you set a min and a max: 5% of 499 UAH gives 30 UAH if the minimum is 30; 5% of a large order hits the maximum. 0 means no limit.
3. Restrict the cart range — “from / to”. The fee won’t apply to orders cheaper or more expensive than the given amounts.
4. Choose a tax class for the line, if the fee needs to be subject to VAT. The line’s sort order must be lower than the sort order of the “Tax” total (5 by default) — the recommended value is 4.
5. At checkout, the customer selects a payment method — the line appears or disappears, the total recalculates, and the same value is written into the order.
6. With Pro you can have as many rules as you like: they’re checked by priority (a lower number means higher priority), and the conditions also include shipping method, product category in the cart, customer group and a date range.

Under the hood

• The standard totals mechanism. This is a full-fledged total-type extension — the line sits alongside “Sub-Total”, “Shipping” and “Tax”, so it lands in the order, emails and reports without any separate workarounds.
• Different signatures in OC3 and OC4. In OpenCart 3.0.5 the total method takes getTotal($total) with a totals / taxes / total array, while OpenCart 4 uses three separate references. The port handles both, so the same calculator gives the same result on both branches.
• Normalising the payment method code. OpenCart 3 stores cod in the session, OpenCart 4 stores cod.cod. The module reduces both formats to the base code, so a rule set up once works on any version.
• No tax surprises. The line can be assigned a tax class, and VAT is calculated from the fee itself — provided the sort order relative to the “Tax” total is correct.

How to install

1. OpenCart 4.x: download cc_codfee.ocmod.zip, install it via “Extensions → Installer”, then “Extensions → Order Totals” → “COD Fee” → “Install” → “Edit”.
2. OpenCart 3.0.x: download cc_codfee-oc3.ocmod.zip, install it via “Extensions → Installer”, refresh the cache in “Extensions → Modifications”, then go to “Extensions → Order Totals”.
3. OpenCart 2.3.x: download cc_codfee-oc2.ocmod.zip, unpack it and upload the contents of the upload/ folder to the store root via FTP or your hosting file manager. The standard 2.3 Installer only copies files over FTP and doesn’t work on most hosting, so installation is manual. Then go to “Extensions → Order Totals” → “Install” → “Edit”. The core isn’t patched: install.xml in the archive only registers the extension in the modifications list.
4. Enable the status, enter the line name (for example “COD Fee”), choose a payment method and set an amount or percentage.
5. Check that the payment method you need is actually installed under “Extensions → Payment” — otherwise it won’t appear in the list.
6. If the fee should be subject to VAT, choose a tax class and set the sort order to 4 (lower than the sort order of the “Tax” line).
7. For Pro: click “Try Pro” — in the window, either take the 7-day trial by email or paste a purchased key on the “I have a key” tab. Once activated, all rules take part in the calculation, not just the basic one; the first matching rule by priority applies.