# Update subscription payment method

Updates the payment method for a subscription contract by refreshing payment instrument from Shopify customer. This endpoint syncs the subscription's payment method with the customer's default payment method in Shopify.

Payment Method Update Process:
- Fetch Latest Payment: Retrieves customer's current default payment method from Shopify
- Update Contract: Associates new payment method with subscription contract
- Validate Payment: Ensures payment method is valid and active
- Sync Changes: Updates payment instrument in subscription billing system

Key Features:
- Automatic Sync: Pulls latest payment method from Shopify customer record
- Payment Validation: Verifies new payment method is usable for billing
- Contract Update: Updates Shopify subscription contract with new payment
- Failed Billing Recovery: Useful for updating payment after billing failures

Use Cases:
- Customer updates credit card and wants to apply to existing subscription
- Recover from failed billing by allowing payment method update
- Sync payment methods in customer portal workflows
- Update expired or invalid payment methods
- Switch between multiple saved payment methods
- Integration with custom payment update flows

Important Notes:
- Customer must have a default payment method in Shopify
- Payment method must be valid and not expired
- Updates are reflected immediately for future billing
- Does not retry failed billing attempts automatically

Authentication: Requires API key authentication via X-API-Key header or api_key parameter

Endpoint: PUT /api/external/v2/subscription-contracts-update-payment-method
Version: 0.0.1

## Query parameters:

  - `contractId` (integer, required)
    Subscription contract ID to update payment method for
    Example: 123456789

  - `api_key` (string)
    API Key (Deprecated - Use Header X-API-Key instead)

## Header parameters:

  - `X-API-Key` (string)


## Response 200 fields

## Response 400 fields

## Response 401 fields

## Response 404 fields

## Response 500 fields