> For the complete documentation index, see [llms.txt](https://apidocs.akinon.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://apidocs.akinon.com/commerce-openapis/checkout/masterpass-payment/select-installment-option-for-masterpass.md). # Select Installment Option for Masterpass Sets the selected installment option for the Masterpass flow. **Required Fields**: * `installment`: Primary key of the installment record to apply. The value must reference an active installment linked to the card resolved in `MasterpassBinNumberPage`. **Validation**: * The submitted installment PK must belong to an active installment for the resolved card. A PK outside this set returns a validation error. **State Update**: * The selected installment is stored on the pre-order. * Any previously selected campaign and reward selections are cleared. **Backward Navigation**: * On backward navigation, the selected installment is cleared. **Next Page**: * `MasterpassOrderNoPage` **available\_for\_post\_order**: `true` ```json {"openapi":"3.1.0","info":{"title":"Overview","version":"1.0.0"},"tags":[{"name":"Masterpass Payment","description":"# Checkout Masterpass Payment\n\nIntegrate the Masterpass digital wallet into your checkout. The flow covers both the standard Masterpass integration and the Masterpass REST variant, including BIN lookup, installment selection, order number assignment, remote installment options, reward selection, and payment completion.\n\n## Authentication\n\nThese endpoints support both authenticated and anonymous sessions.\n\n- **Authenticated users**: Session cookie (`sessionid`) tracks checkout progress.\n- **Anonymous users**: Guest checkout is available when the `CAN_GUEST_PURCHASE` setting is enabled.\n## Request Format\n\nInclude the following header in all checkout requests:\n\n- **x-requested-with**: `XMLHttpRequest`\n\n## Dynamic Settings\n\nThe following settings are managed at runtime through the admin interface and do not require a server restart.\n\n### THREE_D_SECURE_ENABLED\nMaster switch for 3D Secure verification. When disabled, 3D Secure is skipped regardless of other rules.\n\n### THREE_D_SECURE_RULES\nRule-based conditions that determine when 3D Secure is required. When enabled, an amount-based rule is available specifically for Masterpass transactions.\n\n### INSTALLMENT_FILTERS\nFilters that restrict which installment options are presented. Applied during both standard and REST installment selection.\n\n## Static Settings\n\nThe following settings are configured in the server environment and require a restart to take effect.\n\n### DEFAULT_CARD_SLUG\nFallback card identifier used when a BIN number lookup returns no match. Defaults to `other`."}],"servers":[{"description":"Akinon Checkout API","url":"https://{commerce_url}","variables":{"commerce_url":{"default":"sandbox.akinon.com"}}}],"paths":{"/orders/checkout/?page=MasterpassInstallmentPage":{"post":{"tags":["Masterpass Payment"],"operationId":"submitMasterpassInstallment","summary":"Select Installment Option for Masterpass","description":"Sets the selected installment option for the Masterpass flow.\n\n**Required Fields**:\n- `installment`: Primary key of the installment record to apply. The\n value must reference an active installment linked to the card\n resolved in `MasterpassBinNumberPage`.\n\n**Validation**:\n- The submitted installment PK must belong to an active installment\n for the resolved card. A PK outside this set returns a validation\n error.\n\n**State Update**:\n- The selected installment is stored on the pre-order.\n- Any previously selected campaign and reward selections are cleared.\n\n**Backward Navigation**:\n- On backward navigation, the selected installment is cleared.\n\n**Next Page**:\n- `MasterpassOrderNoPage`\n\n**available_for_post_order**: `true`","parameters":[{"$ref":"#/components/parameters/AjaxRequestHeader"},{"$ref":"#/components/parameters/SessionCookieHeader"}],"requestBody":{"required":true,"content":{"application/x-www-form-urlencoded":{"schema":{"$ref":"#/components/schemas/MasterpassInstallmentSelectionInput"}}}},"responses":{"200":{"description":"Installment selected successfully","content":{"application/json":{"schema":{"$ref":"#/components/schemas/CheckoutResponse"}}}}}}}},"components":{"parameters":{"AjaxRequestHeader":{"name":"x-requested-with","in":"header","required":true,"description":"Required header for AJAX requests. Must be set to `XMLHttpRequest` for all checkout requests.","schema":{"type":"string","enum":["XMLHttpRequest"],"default":"XMLHttpRequest"}},"SessionCookieHeader":{"name":"Cookie","in":"header","required":false,"description":"Session cookie header (e.g. `sessionid=abc123` or `osessionid=`)","schema":{"type":"string"}}},"schemas":{"MasterpassInstallmentSelectionInput":{"type":"object","required":["installment"],"properties":{"installment":{"type":"integer","description":"Primary key (`pk`) of the `Installment` record to select. The PK\nmust reference an active installment linked to the card resolved\nin `MasterpassBinNumberPage`."}}},"CheckoutResponse":{"type":"object","properties":{"context_list":{"type":"array","items":{"$ref":"#/components/schemas/PageContext"}},"pre_order":{"$ref":"#/components/schemas/PreOrder"},"errors":{"oneOf":[{"type":"object","additionalProperties":{"type":"array","items":{"type":"string"}}},{"type":"null"},{"type":"array","items":{"type":"string"}}]},"template_name":{"type":"string"}}},"PageContext":{"type":"object","properties":{"page_name":{"type":"string","description":"Class name of the page (e.g., \"IndexPage\", \"AddressSelectionPage\")"},"page_slug":{"type":"string","description":"URL-friendly slug for the page"},"page_context":{"type":"object","description":"Page-specific context data","additionalProperties":true}}},"PreOrder":{"type":"object","description":"Pre-order state containing basket, addresses, shipping, payment 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shipping option with calculated amount","properties":{"pk":{"type":"integer"},"name":{"type":"string"},"slug":{"type":"string"},"logo":{"oneOf":[{"type":"string","format":"uri"},{"type":"null"}]},"shipping_amount":{"type":"string","pattern":"^\\d+\\.\\d{2}$"},"description":{"oneOf":[{"type":"string"},{"type":"null"}]},"kwargs":{"type":"object","additionalProperties":true}}},"PaymentOptionDetail":{"type":"object","description":"Detailed payment option with type information","properties":{"pk":{"type":"integer"},"name":{"type":"string"},"slug":{"type":"string"},"payment_type":{"type":"string","enum":["credit_card","funds_transfer","bkm_express","loyalty_money","cash_register","gpay","redirection","stored_card","masterpass","masterpass_rest","credit_payment","pay_later","saved_card","confirmation","b2b","wallet","pay_on_delivery"]},"payment_type_label":{"type":"string"}}},"Installment":{"type":"object","properties":{"pk":{"type":"integer"},"installment_count":{"type":"integer"},"label":{"type":"string"},"price_with_accrued_interest":{"type":"string","pattern":"^\\d+\\.\\d{2}$"},"monthly_price_with_accrued_interest":{"type":"string","pattern":"^\\d+\\.\\d{2}$"}}},"DeliveryOption":{"type":"object","properties":{"pk":{"type":"integer"},"name":{"type":"string"},"delivery_option_type":{"type":"string","enum":["customer","retail_store","pickup_location"]},"is_active":{"type":"boolean"}}},"RetailStore":{"type":"object","properties":{"pk":{"type":"integer"},"name":{"type":"string"},"erp_code":{"type":"string"},"township":{"$ref":"#/components/schemas/Township"},"click_and_collect":{"type":"boolean"},"is_active":{"type":"boolean"}}},"BankAccount":{"type":"object","description":"Bank account for funds transfer payments","properties":{"pk":{"type":"integer"},"bank_name":{"type":"string","description":"Name of the bank"},"account_holder":{"type":"string","description":"Account holder name"},"iban":{"type":"string","description":"International Bank Account Number"},"currency":{"type":"string","description":"Currency code (e.g., \"USD\", \"EUR\", \"TRY\")"},"is_active":{"type":"boolean"}}},"PaymentChoice":{"type":"object","properties":{"value":{"type":"string"},"label":{"type":"string"},"price":{"type":"string","pattern":"^\\d+\\.\\d{2}$"}}},"DataSourceShippingOptionDetail":{"type":"object","description":"Data source shipping option for multi-vendor shipping","properties":{"pk":{"type":"integer"},"shipping_amount":{"type":"string","pattern":"^\\d+\\.\\d{2}$"},"shipping_option_name":{"type":"string"},"shipping_option_logo":{"oneOf":[{"type":"string","format":"uri"},{"type":"null"}]},"data_source":{"type":"object","properties":{"pk":{"type":"integer"},"title":{"type":"string"}}},"description":{"oneOf":[{"type":"string"},{"type":"null"}]}}},"PreOrderAttributeBasedShippingOption":{"type":"object","description":"Attribute-based shipping option selected for a product group","properties":{"pk":{"type":"integer"},"shipping_option_name":{"type":"string"},"shipping_option_logo":{"oneOf":[{"type":"string","format":"uri"},{"type":"null"}]},"shipping_amount":{"type":"string","pattern":"^\\d+\\.\\d{2}$"},"product_ids":{"type":"array","items":{"type":"integer"}},"attribute_value":{"type":"string"},"attribute_key":{"oneOf":[{"type":"array","items":{"type":"string"}},{"type":"null"}]}}}}}} ``` --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://apidocs.akinon.com/commerce-openapis/checkout/masterpass-payment/select-installment-option-for-masterpass.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. 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