> ## Documentation Index > Fetch the complete documentation index at: https://docs.polygon.technology/llms.txt > Use this file to discover all available pages before exploring further. # Create a Counterparty > Create a Counterparty. ## OpenAPI ````yaml /api-reference/openapi.yaml post /counterparties openapi: 3.0.3 info: title: Polygon OMS Public API version: v26.05.28-0001 description: >- Unified API for moving money between crypto and fiat. Three ways to move money: Transactions (instant, wallet or card funded, including Cash-In for in-person cash deposits), Deposit Addresses (reusable crypto deposit configurations), and Virtual Accounts (dedicated bank accounts that auto-convert fiat to crypto). Standard transactions follow a two-step flow: create a Quote (pricing), then create a Transaction (execution). Cash-in codes generate a one-time deposit code for in-person cash deposits at retail locations. contact: name: Polygon OMS url: https://oms.polygon.technology servers: - url: https://sandbox-api.polygon.technology/v0.12 description: Sandbox - url: https://api.polygon.technology/v0.12 description: Production security: - BearerAuth: [] tags: - name: Auth description: Authentication via FrontEgg - name: Customers description: Customer management and KYC - name: Customer - name: Wallet - name: Quote - name: Transaction - name: CashIns - name: CashLocation - name: Sandbox - name: VirtualAccount - name: Counterparty - name: ExternalAccount - name: Reference - name: DepositAddress paths: /counterparties: post: tags: - Counterparty summary: Create a Counterparty description: Create a Counterparty. operationId: createCounterparty parameters: - $ref: '#/components/parameters/IdempotencyKeyHeader' requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CounterpartyCreateRequest' responses: '201': description: >- The request has succeeded and a new resource has been created as a result. content: application/json: schema: $ref: '#/components/schemas/Counterparty' components: parameters: IdempotencyKeyHeader: name: Idempotency-Key in: header required: true description: >- Required on POST and PUT requests. Use a unique value per logical mutation attempt, for example a UUID. schema: type: string schemas: CounterpartyCreateRequest: type: object required: - customerId - name - address properties: customerId: type: string description: Owning customer (cst_… TypeID or legacy public id). name: type: string minLength: 1 maxLength: 140 description: Full legal name or registered business name. 1..140 chars. entityType: allOf: - $ref: '#/components/schemas/CounterpartyEntityType' description: '`individual` or `business`.' address: allOf: - $ref: '#/components/schemas/Address' description: |- Registered address. Required: must include non-blank line1, city, zipCode and a two-letter ISO country (state required for US). email: type: string description: Contact email address. phone: type: string description: Phone in E.164 format. taxId: type: string description: >- Tax ID (CPF, CNPJ, SSN, etc.). Required for some external-account types. dateOfBirth: type: string format: date description: Date of birth (YYYY-MM-DD). nationality: type: string description: ISO 3166-1 alpha-2. metadata: type: object additionalProperties: type: string description: >- Free-form key-value pairs stored on the resource and echoed back on reads. example: customerId: cst_vfa0nxw6zvyws9g237jrxn4y7k name: Alice Smith entityType: individual address: line1: 500 Market Street city: San Francisco state: CA country: US zipCode: '94105' email: alice@example.com phone: '+14155550100' nationality: US Counterparty: type: object required: - address properties: id: $ref: '#/components/schemas/typeId' object: type: string enum: - counterparty customerId: $ref: '#/components/schemas/typeId' status: $ref: '#/components/schemas/CounterpartyStatus' rejectionReason: type: string description: Set when status = `rejected`. name: type: string description: Full legal name or registered business name. entityType: $ref: '#/components/schemas/CounterpartyEntityType' address: allOf: - $ref: '#/components/schemas/Address' description: >- Registered address. Required since v0.11 — always present in responses. email: type: string phone: type: string taxId: type: string dateOfBirth: type: string format: date nationality: type: string description: ISO 3166-1 alpha-2. metadata: type: object additionalProperties: type: string createdAt: type: string format: date-time updatedAt: type: string format: date-time description: |- A third party a customer transacts with — an entry in the customer's address book. Counterparties will own External Accounts (registered payment destinations) in a later slice. CounterpartyEntityType: type: string enum: - individual - business Address: type: object properties: line1: type: string description: Street address, line 1. line2: type: string description: Street address, line 2. city: type: string description: City. state: type: string description: State / province / region. country: type: string description: ISO 3166-1 alpha-2 zipCode: type: string description: ZIP / postal code. description: A postal address. country is an ISO 3166-1 alpha-2 country code. typeId: type: string pattern: >- ^[a-z]+_([0-9a-hjkmnp-tv-z]{26}|[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})$ description: >- Public TypeID, e.g. `txn_01h455vb4pex5vsknk084sn02q`; legacy UUID suffixes are accepted until non-v7 rows are retired. x-go-type: string CounterpartyStatus: type: string enum: - active - rejected - deleted description: |- Lifecycle of a counterparty. `rejected` is reserved for create-time compliance screening (not yet active); `deleted` marks a soft-deleted record that remains readable by id. securitySchemes: BearerAuth: type: http scheme: bearer bearerFormat: JWT description: Token from POST /auth/token ````