> ## Documentation Index > Fetch the complete documentation index at: https://developers.appstle.com/llms.txt > Use this file to discover all available pages before exploring further. # Add one-time product to upcoming order > Adds a one-time product (one-off) to a specific upcoming billing attempt for a membership contract. The product will be included only in the specified order and will not become part of the recurring subscription. **Key Features:** - **One-Time Addition**: Product added to single order only - **Billing Cycle Targeting**: Specify exact order to add item to - **No Subscription Impact**: Doesn't change recurring items - **Instant Upsell**: Add products between regular billing cycles - **Customer Flexibility**: Allow members to add extras to next order - **Activity Logging**: Tracks who added the item (merchant vs API) **Required Parameters:** - **Contract ID**: Target subscription contract - **Billing Attempt ID**: Specific upcoming order to add item to - **Variant ID**: Shopify product variant to add - **Variant Handle**: Product handle for identification **How It Works:** 1. Validates contract exists and belongs to shop 2. Checks if contract is not frozen (minimum cycles) 3. Verifies billing attempt is upcoming (not already processed) 4. Adds variant to the specified billing attempt 5. Returns updated list of all one-offs for the contract 6. Logs activity for audit trail **Use Cases:** - Customer wants to add a bonus product to next delivery - Merchant offers limited-time add-on to existing members - Trial/sample products added to specific orders - Holiday specials or seasonal items - Promotional gifts or rewards - One-time upsells in customer portal **Business Rules:** - Item added only to specified billing attempt - Cannot add to past or completed orders - Contract must not be frozen/minimum cycle locked - Duplicate items increment quantity **Authentication:** Requires API key authentication via X-API-Key header or api_key parameter ## OpenAPI ````yaml /memberships/admin-api-swagger.json put /api/external/v2/subscription-contract-one-offs-by-contractId-and-billing-attempt-id openapi: 3.0.1 info: description: >- Comprehensive API documentation for managing memberships, payments, and related operations. These APIs allow you to programmatically manage membership lifecycles, handle payments, configure products, and integrate membership functionality into your applications. title: Admin APIs version: 0.0.1 servers: - url: https://membership-admin.appstle.com security: [] tags: - description: >- APIs for managing Shopify delivery profiles, shipping rates, zones, and free shipping configuration for subscription memberships name: Shipping & Delivery Profiles - description: >- APIs for retrieving historical discount code usage and redemption information for membership contracts name: Customer Discount History - description: >- APIs for managing membership cancellation flow settings including retention offers, survey questions, and cancel confirmation screens name: Cancellation Flow Configuration - description: >- APIs for managing membership billing attempts, recurring orders, payment retries, order history, and order skipping name: Billing & Orders - description: >- APIs for managing one-time product additions to upcoming subscription orders, including adding, retrieving, and removing one-off items name: One-Time Add-Ons - description: >- APIs for managing membership/subscription plan groups, including creating plans, configuring discounts, billing intervals, and assigning products to plans name: Membership Plans - description: >- APIs for managing subscription product bundles, bundle configurations, item grouping, and bundle-specific discount codes name: Product Bundles - description: >- APIs for retrieving custom CSS styles applied to subscription widgets and customer portal for theme customization name: Custom CSS Styling - description: >- APIs for managing customer portal settings including UI customization, text labels, feature toggles, and branding options for the member self-service portal name: Customer Portal Configuration - description: >- APIs for managing membership/subscription contracts including creation, updates, status changes, line items, discounts, and billing operations name: Membership Contracts - description: >- APIs for managing subscription bundle configuration settings including bundle behavior, pricing rules, and display options name: Bundle Settings - description: >- APIs for managing customer payment methods, payment tokens, and payment method retrieval for subscriptions name: Customer Payment Methods - description: >- APIs for retrieving product swap/substitution options allowing members to exchange subscription items based on configured swap rules and variant groups name: Product Swap Rules - description: >- APIs for retrieving product catalog, variants, pricing, and inventory information for subscription memberships. name: Product & Inventory Data - description: >- APIs for managing shop-level membership settings, configuration, and general store information. name: Shop Settings - description: >- APIs for performing bulk/mass operations on multiple membership contracts including status updates, product replacements, and billing date changes. name: Bulk Operations paths: /api/external/v2/subscription-contract-one-offs-by-contractId-and-billing-attempt-id: put: tags: - One-Time Add-Ons summary: Add one-time product to upcoming order description: >- Adds a one-time product (one-off) to a specific upcoming billing attempt for a membership contract. The product will be included only in the specified order and will not become part of the recurring subscription. **Key Features:** - **One-Time Addition**: Product added to single order only - **Billing Cycle Targeting**: Specify exact order to add item to - **No Subscription Impact**: Doesn't change recurring items - **Instant Upsell**: Add products between regular billing cycles - **Customer Flexibility**: Allow members to add extras to next order - **Activity Logging**: Tracks who added the item (merchant vs API) **Required Parameters:** - **Contract ID**: Target subscription contract - **Billing Attempt ID**: Specific upcoming order to add item to - **Variant ID**: Shopify product variant to add - **Variant Handle**: Product handle for identification **How It Works:** 1. Validates contract exists and belongs to shop 2. Checks if contract is not frozen (minimum cycles) 3. Verifies billing attempt is upcoming (not already processed) 4. Adds variant to the specified billing attempt 5. Returns updated list of all one-offs for the contract 6. Logs activity for audit trail **Use Cases:** - Customer wants to add a bonus product to next delivery - Merchant offers limited-time add-on to existing members - Trial/sample products added to specific orders - Holiday specials or seasonal items - Promotional gifts or rewards - One-time upsells in customer portal **Business Rules:** - Item added only to specified billing attempt - Cannot add to past or completed orders - Contract must not be frozen/minimum cycle locked - Duplicate items increment quantity **Authentication:** Requires API key authentication via X-API-Key header or api_key parameter operationId: saveOneOffByV2 parameters: - description: API Key (Deprecated - Use Header X-API-Key instead) in: query name: api_key required: false schema: type: string - in: header name: X-API-Key required: false schema: type: string - description: Subscription contract ID example: 123456 in: query name: contractId required: true schema: format: int64 type: integer - description: Billing attempt ID to add the item to example: 789012 in: query name: billingAttemptId required: true schema: format: int64 type: integer - description: Product variant ID to add example: 456789 in: query name: variantId required: true schema: format: int64 type: integer - description: Product handle for identification example: coffee-beans-1lb in: query name: variantHandle required: true schema: type: string responses: '200': content: application/json: schema: items: $ref: '#/components/schemas/SubscriptionContractOneOffDTO' type: array description: >- One-off product successfully added, returns updated list of all one-offs '400': content: application/json: examples: Frozen Contract: description: Frozen Contract value: detail: >- Cannot modify contract frozen until minimum cycles completed errorKey: frozen_contract status: 400 title: Bad Request Invalid Billing Attempt: description: Invalid Billing Attempt value: detail: Billing attempt not found or already processed errorKey: invalid_billing_attempt status: 400 title: Bad Request description: Invalid request or business rule violation '401': content: '*/*': schema: items: $ref: '#/components/schemas/SubscriptionContractOneOffDTO' type: array description: Authentication required - invalid or missing API key '403': content: '*/*': schema: items: $ref: '#/components/schemas/SubscriptionContractOneOffDTO' type: array description: Access forbidden - contract does not belong to authenticated shop '404': content: '*/*': schema: items: $ref: '#/components/schemas/SubscriptionContractOneOffDTO' type: array description: Contract or variant not found components: schemas: SubscriptionContractOneOffDTO: properties: billingAttemptId: description: Associated billing attempt ID format: int64 type: integer id: description: Unique identifier of the one-off item example: 789 format: int64 type: integer shop: description: Shop domain identifier example: my-store.myshopify.com type: string subscriptionContractId: description: Associated subscription contract ID format: int64 type: integer variantHandle: description: Product variant handle for the one-off item type: string variantId: description: Shopify product variant ID of the one-off item format: int64 type: integer required: - shop type: object ````