post
https://api.fastspring.com/subscriptions/estimate
Generates a preview of the estimated charges, credits, or refunds for a subscription before making any changes.
This endpoint returns a prorated estimate for only one subscription per request.
How to use the Try It feature
Use the built-in API explorer to test this endpoint directly in your browser.
| Task | Instructions |
|---|---|
| Authenticate | Locate the CREDENTIALS section on the right. Enter your username and password to ensure the request is authorized. |
| Select Example | Use the EXAMPLES drop-down menu to load a pre-configured request body. The JSON payload will update automatically. |
| Customize Data | Modify the JSON fields in the BODY PARAMS section. Your changes update the request preview instantly. |
| Execute | Click the Try It! button to send the API request and view the real-time response below. |
Request body examples and use cases
Select a request body example
All of the request examples listed below can be selected from the EXAMPLES drop-down menu in the top-right corner of the Try It! feature.
| Request Example | Use Case |
|---|---|
| Estimate Subscription | Estimate the total cost of a subscription, including the base product, add-ons, pricing in multiple currencies, proration, and applied coupons. |
| Upgrade Plan | Upgrade a subscription from a lower-tier plan (e.g., "basic") to a higher-tier premium plan. |
| Downgrade Plan | Downgrade a subscription from a higher-tier plan (e.g., "premium") to a lower-tier basic plan. |
| Add-On Quantity Change | Increase the quantity of an existing add-on in a subscription. |
| Complex Subscription Change | Modify multiple aspects of a subscription at the same time, including:
|
Error handling
This table lists errors you may encounter when working with this endpoint and provides solutions to help you troubleshoot.
| Status | Error Message | Solution |
|---|---|---|
400 |
Request must contain a single root object. |
Ensure the request payload contains a single root object. |
400 |
Request must contain a subscription ID. |
Ensure the subscription ID is included in your request payload. |
400 |
Proration is not allowed for this subscription. |
Check the subscription's eligibility for proration. |
400 |
Refund exceeds the last charge amount. |
Ensure the refund amount does not exceed the last charge amount. |
404 |
Subscription ID does not exist: `[{subscriptionId}]` |
Verify the subscription ID is correct and exists. |
500 |
Subscription is not changeable |
Verify that the subscriptionID is changeable, or try again with a different subscription. |