Articles on: Troubleshooting

Deposit is not applying to product option add-ons

If you have set up a deposit on a product but add-on fees from a product options app are being charged in full at checkout instead of being split, this guide will help you find the cause and fix it.

Why this happens

Downpay calculates a deposit based on the products and variants assigned to a purchase option. For add-on fees created by other apps to be included in the deposit percentage, three things need to be true:

The options app must be compatible with Downpay
Each paid add-on product must exist as a real product or variant in Shopify and be added to the same Downpay purchase option as the base product
The deposit must be set as a percentage, not a fixed amount
The customer must land on the full cart page before checkout, not the cart drawer alone

If any of these are not in place, Downpay cannot partially charge the add-on fees and charges them in full. Work through the steps below in order to find where the setup has broken down.

Step 1: Check if your app is compatible

Before anything else, confirm your product options app actually works with Downpay. This is the most common reason add-ons get charged in full, and there is no point adjusting your Downpay setup if the app itself is the blocker.

See our product options apps compatibility guide for a list of top recommended options apps and any required settings changes. We also try and maintain our compatibility list.

Apps that use Shopify's Cart Transform API or draft orders on the backend are not compatible with Downpay at this time. The compatibility guide explains what to look for and which apps have settings you can change to restore compatibility.

If your app is not on the list or in the guide, contact our support team and we can test it with you.

If your app is compatible, continue to Step 2.

Step 2: Check your purchase option includes the add-ons

For Downpay to split the cost of an add-on, that add-on must be assigned to the same Downpay purchase option as the base product.

Open the Downpay app in your Shopify admin

Open the purchase option that applies to your base product

Check that each paid option product or variant is listed in the same purchase option alongside the base product

If any are missing, add them and save

If your purchase option already includes all add-ons, continue to Step 3.

Step 3: Check your deposit is percentage-based

Deposits on Shopify are calculated per line item. Because of this, Downpay can only calculate a deposit accurately across a base product and its add-ons when the deposit is set as a percentage.

Open the relevant purchase option in Downpay

Check that the deposit type is set to percentage and not a fixed amount

If it is set to a fixed amount, switch it to percentage and save

If your deposit is already percentage-based, continue to Step 4.

Step 4: Check customers are reaching the cart page

Downpay calculates the deposit across the main product and add-on options products on the cart page when the Downpay cart embed is enabled. If your store sends customers directly to checkout and bypasses the cart page, Downpay may not have a chance to apply the deposit to the add-on fees.

Check that your theme to ensure the Downpay cart subtotals embed is enabled and that you are not skipping the cart page for products that use paid options. If they are, update the add to cart flow to route customers through the cart first.

If you have worked through all four steps and the issue is still happening, get in touch and we will help you troubleshoot further.

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Updated on: 15/04/2026

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