CartModules: Order Additional Fees

Add a service, handling, or convenience fee to every order

Order Additional Fees lets your store add an extra charge to every order — a service fee, processing charge, handling fee, or convenience fee. You decide what to call it, how much to charge, and whether it is a flat amount or a percentage of the order. The fee is added on its own while the customer is checking out and shows as its own line in the checkout summary, so shoppers see exactly what they are paying for before they confirm.

After the order is placed, the fee appears on the order details page for both the customer and the store admin, and on order documents like invoices and receipts. The fee value is saved with each order, so your records always show the exact amount the customer paid — even if you change the setting later. It is also available in the storefront API response, so mobile apps and headless storefronts can show it too. Works on CS-Cart Store Builder and Multi-Vendor, single or multiple storefronts.

Key Features

• One Extra Fee Line — adds a single, clearly labelled fee to every order
• Flat or Percentage — charge a fixed amount (e.g. 2.50) or a percentage (e.g. 5%)
• Subtotal or Total Basis — percentage fees can be worked out from the products subtotal or the full order total
• Custom Label — you choose the wording customers see: Service Fee, Handling Fee, Processing Charge, or anything that fits your store
• Shown at Checkout — appears as its own line in the checkout summary before the customer pays
• On Order Details & Admin — visible on the customer’s order page and the admin order screen
• On Invoices & Documents — included on invoices and other order documents
• API / Headless Ready — available in the storefront response for mobile apps and headless storefronts
• Saved per Order — the charged amount is stored on each order, so older orders keep the value actually paid
• Easy On/Off — set the fee amount to zero to switch it off without uninstalling

How It Works

1. The admin opens the addon settings and enters a fee label, a fee amount, and whether percentage fees apply to the subtotal or total
2. A customer adds products to the cart and goes to checkout
3. The addon works out the fee — the flat amount, or the percentage applied to subtotal or total — and adds it to the order
4. The customer sees the fee as its own line in the checkout summary, with your label, and the order total updates
5. The customer places the order and pays the new total
6. The fee is saved with the order and appears on the order details page, the admin order screen, and on invoices and documents
7. If you change the fee later, existing orders keep the amount first charged — only new orders use the new setting

Requirements

• CS-Cart Store Builder or Multi-Vendor (single or multiple storefronts) 4.6.3 or higher
• PHP 7.4 or higher (tested up to PHP 8.3)

Installation

1. Go to Add-ons > Manage add-ons, click Manual installation, and upload the addon zip file
2. Activate the addon and enter the license key
3. Open the addon’s General Settings, set your fee label, amount, and calculation basis (see Configuration below), and save — the fee applies to new orders right away

Configuration Options

Support

For questions, issues, or feature requests, contact us at www.cartmodules.com.