---
title: "Apply custom upgrade"
method: POST
path: "/2026-04/subscription/{subscriptionId}/upgrade/custom"
---

# Apply custom upgrade

`POST /2026-04/subscription/{subscriptionId}/upgrade/custom`

## Request

- Base URL: `https://api.loopsubscriptions.com/storefront`
- URL: `https://api.loopsubscriptions.com/storefront/2026-04/subscription/{subscriptionId}/upgrade/custom`
- Auth: API key in header `Authorization`

This endpoint allows to apply a custom upgrade to an existing line of a subscription by changing its product, quantity, billing frequency, delivery frequency, and pricing configuration

## Path parameters

- `subscriptionId` string, required

## Request body

- object
  - `oldLineId` integer, required: ID of the existing subscription line that needs to be upgraded
  - `newVariantShopifyId` integer, required: Shopify variant ID of the new product
  - `quantity` integer, required: Quantity of the new product
  - `customDiscount` object: Discount to be applied on new product
    - `type` 'NONE' | 'FIXED_PRICE' | 'PERCENTAGE' | 'PRICE': Type of discount to be applied on the base price of the new product
    - `value` number, float: Value of discount type
  - `billingPolicy` object
    - `interval` 'WEEK' | 'MONTH' | 'YEAR'
    - `intervalCount` integer
  - `deliveryPolicy` object
    - `interval` 'WEEK' | 'MONTH' | 'YEAR'
    - `intervalCount` integer
  - `sellingPlanId` integer: Loop ID of the selling plan that needs to be applied to the product

## Response `200`

The upgrade has been applied successfully

- object
  - `success` boolean
  - `message` string
  - `data` unknown
  - `code` string
  - `pageInfo` unknown

## Changes

- **2026-11-03** `1ff6a5700816`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/loopwork/apis/storefront-api/changes/2026-04/subscription/:subscriptionId/upgrade/custom/post.md)

---

[API](https://skmtc.dev/loopwork/apis/storefront-api.md) - [All operations](https://skmtc.dev/loopwork/apis/storefront-api/llms.txt) - [OpenAPI document](https://skmtc.dev/loopwork/apis/storefront-api/revisions/1ff6a5700816?raw)