# Add a contract to an existing customer

Required Scopes: 

Endpoint: POST /v1/memberships/customers/{customerId}/add-membership
Version: 1.27.0
Security: ApiKeyAuth

## Path parameters:

  - `customerId` (integer, required)

## Request fields (application/json):

  - `contractOfferTermId` (integer, required)
    Unique ID of the contract offer term
    Example: 1000

  - `startDate` (string, required)
    The start date of the contract
    Example: "2026-02-01"

  - `preuseDate` (string)
    The pre use date of the contract. If not provided, it will be evaluated based on contract offer configuration.
    Example: "2026-01-01"

  - `notes` (string)
    The notes related to the contract
    Example: "Some notes"

  - `thirdPartyId` (string)
    Unique ID of the third party contract in the third party system
    Example: "1000a"

  - `employeeId` (integer)
    Unique ID of the employee who created the membership
    Example: 1239812733

  - `referralCode` (string)
    Referral code to link with recruiter
    Example: "A500D"

  - `selectedSelectableModuleIds` (array)
    The selected modules from the available selectable modules

  - `selectedOptionalModuleIds` (array)
    The selected modules from the available optional modules

  - `initialPaymentRequestToken` (string)
    This token identifies a pre-authorized payment request. It acts as a reference to the payment session initiated by the user. It's not needed for preview endpoints.
    Example: "3JtyH5sakfn2V22vB0napNC2zWMlpFwS9gPQawuk7Jw1F00atOD0BA"

  - `contractSignature` (object)
    The signature SVG for the contract document

  - `contractSignature.base64SvgSignature` (string, required)
    Customer confirmation signature SVG value as base 64 string

  - `legalRepresentative` (object)
    The legal representative information used for add-membership and membership preview requests. For the customer signup request, the top-level legalRepresentative field remains the primary field and this contract field is only used as a fallback.

  - `legalRepresentative.type` (string, required)
    Type of the legal representative
    Enum: "EXTERNAL_PERSON", "EXISTING_CUSTOMER"

  - `legalRepresentative.person` (object)
    External person data used when type is EXTERNAL_PERSON

  - `legalRepresentative.person.firstName` (string, required)
    First name of the legal representative
    Example: "Erika"

  - `legalRepresentative.person.secondFirstName` (string)
    Second first name of the legal representative
    Example: "Maria"

  - `legalRepresentative.person.lastName` (string, required)
    Last name of the legal representative
    Example: "Mustermann"

  - `legalRepresentative.person.secondLastName` (string)
    Second last name of the legal representative
    Example: "Meyer"

  - `legalRepresentative.person.dateOfBirth` (string)
    Date of birth of the legal representative
    Example: "1985-08-24"

  - `legalRepresentative.person.placeOfBirth` (string)
    Place of birth of the legal representative
    Example: "Hamburg"

  - `legalRepresentative.person.countryOfBirth` (string)
    Country of birth of the legal representative
    Example: "DE"

  - `legalRepresentative.person.gender` (string)
    Gender of the legal representative
    Enum: "MALE", "FEMALE", "UNISEX"

  - `legalRepresentative.person.email` (string)
    Email address of the legal representative
    Example: "legal.rep@example.com"

  - `legalRepresentative.person.phoneNumberPrivate` (string)
    Private phone number of the legal representative
    Example: "+44123456789"

  - `legalRepresentative.person.phoneNumberMobile` (string)
    Mobile phone number of the legal representative
    Example: "+44987654321"

  - `legalRepresentative.person.street` (string, required)
    Street of the legal representative address
    Example: "Raboisen Street"

  - `legalRepresentative.person.houseNumber` (string)
    House number of the legal representative address
    Example: "3-4"

  - `legalRepresentative.person.additionalAddressInformation` (string)
    Additional address information of the legal representative
    Example: "2nd floor"

  - `legalRepresentative.person.city` (string, required)
    City of the legal representative address
    Example: "Hamburg"

  - `legalRepresentative.person.zipCode` (string, required)
    Zip code of the legal representative address
    Example: "220-99"

  - `legalRepresentative.person.countryCode` (string, required)
    Country code of the legal representative address
    Example: "DE"

  - `legalRepresentative.customerId` (integer)
    Customer id used when type is EXISTING_CUSTOMER
    Example: 98765

  - `legalRepresentative.singleParent` (boolean)
    Whether the provided legal representative is the only legal guardian
    Example: true

  - `legalRepresentative.addressToLiablePerson` (boolean)
    Whether communication and billing should be sent to the legal representative

  - `legalRepresentative.legalRepresentativeSignature` (object)
    The first legal representative signature SVG for the contract document
    Example: {"base64SvgSignature":"PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciLz4="}

  - `legalRepresentative.legalRepresentativeSignatureSecondPerson` (object)
    The second legal representative signature SVG for the contract document
    Example: {"base64SvgSignature":"PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciLz4="}

  - `textBlockSignatures` (array)
    Signatures for text blocks

  - `textBlockSignatures.base64SvgSignature` (string, required)
    Text block's signature SVG value as base 64 string

  - `textBlockSignatures.textBlockId` (integer, required)
    The ID of the referenced text block of the signature

  - `voucherCode` (string)
    An optional code for a voucher. Only credit and discount vouchers are supported.
    Example: 123

## Response 400 fields (application/json):

  - `errorMessage` (string, required)
    Resolved message in the context-specific default locale

  - `errorCode` (string)
    Key for translation files

  - `traceId` (string)
    Datadog trace id

  - `reference` (string)
    Reference to validation error
    Example: "parent.child"

  - `args` (array)
    Arguments referenced by format specifiers while resolving the message from translation files

  - `typedArgs` (array)
    Same as  but with type information

  - `typedArgs.value` (object)

  - `typedArgs.type` (string)
    Enum: "TIMESTAMP", "BOOLEAN", "DATE", "MONTH_DAY", "TIME", "TERM", "TERM_LIST", "INTEGER", "DECIMAL", "STRING", "MONEY", "LIMITABLE_CONFIG_PROPERTY", "I18N_KEY", "I18N_KEY_LIST", "PERMISSION_LIST", "ENUM", "AVAILABILITY_LIST"

## Response 401 fields (application/json):

  - `errorMessage` (string, required)
    Resolved message in the context-specific default locale

  - `errorCode` (string)
    Key for translation files

  - `traceId` (string)
    Datadog trace id

  - `reference` (string)
    Reference to validation error
    Example: "parent.child"

  - `args` (array)
    Arguments referenced by format specifiers while resolving the message from translation files

  - `typedArgs` (array)
    Same as  but with type information

  - `typedArgs.value` (object)

  - `typedArgs.type` (string)
    Enum: "TIMESTAMP", "BOOLEAN", "DATE", "MONTH_DAY", "TIME", "TERM", "TERM_LIST", "INTEGER", "DECIMAL", "STRING", "MONEY", "LIMITABLE_CONFIG_PROPERTY", "I18N_KEY", "I18N_KEY_LIST", "PERMISSION_LIST", "ENUM", "AVAILABILITY_LIST"

## Response 403 fields (application/json):

  - `errorMessage` (string, required)
    Resolved message in the context-specific default locale

  - `errorCode` (string)
    Key for translation files

  - `traceId` (string)
    Datadog trace id

  - `reference` (string)
    Reference to validation error
    Example: "parent.child"

  - `args` (array)
    Arguments referenced by format specifiers while resolving the message from translation files

  - `typedArgs` (array)
    Same as  but with type information

  - `typedArgs.value` (object)

  - `typedArgs.type` (string)
    Enum: "TIMESTAMP", "BOOLEAN", "DATE", "MONTH_DAY", "TIME", "TERM", "TERM_LIST", "INTEGER", "DECIMAL", "STRING", "MONEY", "LIMITABLE_CONFIG_PROPERTY", "I18N_KEY", "I18N_KEY_LIST", "PERMISSION_LIST", "ENUM", "AVAILABILITY_LIST"

## Response 404 fields (application/json):

  - `errorMessage` (string, required)
    Resolved message in the context-specific default locale

  - `errorCode` (string)
    Key for translation files

  - `traceId` (string)
    Datadog trace id

  - `reference` (string)
    Reference to validation error
    Example: "parent.child"

  - `args` (array)
    Arguments referenced by format specifiers while resolving the message from translation files

  - `typedArgs` (array)
    Same as  but with type information

  - `typedArgs.value` (object)

  - `typedArgs.type` (string)
    Enum: "TIMESTAMP", "BOOLEAN", "DATE", "MONTH_DAY", "TIME", "TERM", "TERM_LIST", "INTEGER", "DECIMAL", "STRING", "MONEY", "LIMITABLE_CONFIG_PROPERTY", "I18N_KEY", "I18N_KEY_LIST", "PERMISSION_LIST", "ENUM", "AVAILABILITY_LIST"

## Response 409 fields (application/json):

  - `errorMessage` (string, required)
    Resolved message in the context-specific default locale

  - `errorCode` (string)
    Key for translation files

  - `traceId` (string)
    Datadog trace id

  - `reference` (string)
    Reference to validation error
    Example: "parent.child"

  - `args` (array)
    Arguments referenced by format specifiers while resolving the message from translation files

  - `typedArgs` (array)
    Same as  but with type information

  - `typedArgs.value` (object)

  - `typedArgs.type` (string)
    Enum: "TIMESTAMP", "BOOLEAN", "DATE", "MONTH_DAY", "TIME", "TERM", "TERM_LIST", "INTEGER", "DECIMAL", "STRING", "MONEY", "LIMITABLE_CONFIG_PROPERTY", "I18N_KEY", "I18N_KEY_LIST", "PERMISSION_LIST", "ENUM", "AVAILABILITY_LIST"

## Response 429 fields (application/json):

  - `errorMessage` (string, required)
    Resolved message in the context-specific default locale

  - `errorCode` (string)
    Key for translation files

  - `traceId` (string)
    Datadog trace id

  - `reference` (string)
    Reference to validation error
    Example: "parent.child"

  - `args` (array)
    Arguments referenced by format specifiers while resolving the message from translation files

  - `typedArgs` (array)
    Same as  but with type information

  - `typedArgs.value` (object)

  - `typedArgs.type` (string)
    Enum: "TIMESTAMP", "BOOLEAN", "DATE", "MONTH_DAY", "TIME", "TERM", "TERM_LIST", "INTEGER", "DECIMAL", "STRING", "MONEY", "LIMITABLE_CONFIG_PROPERTY", "I18N_KEY", "I18N_KEY_LIST", "PERMISSION_LIST", "ENUM", "AVAILABILITY_LIST"

## Response 500 fields (application/json):

  - `errorMessage` (string, required)
    Resolved message in the context-specific default locale

  - `errorCode` (string)
    Key for translation files

  - `traceId` (string)
    Datadog trace id

  - `reference` (string)
    Reference to validation error
    Example: "parent.child"

  - `args` (array)
    Arguments referenced by format specifiers while resolving the message from translation files

  - `typedArgs` (array)
    Same as  but with type information

  - `typedArgs.value` (object)

  - `typedArgs.type` (string)
    Enum: "TIMESTAMP", "BOOLEAN", "DATE", "MONTH_DAY", "TIME", "TERM", "TERM_LIST", "INTEGER", "DECIMAL", "STRING", "MONEY", "LIMITABLE_CONFIG_PROPERTY", "I18N_KEY", "I18N_KEY_LIST", "PERMISSION_LIST", "ENUM", "AVAILABILITY_LIST"