---
title: "Attach Documents to Business Customer V2"
method: POST
path: "/v2/customers/{customer_id}/business/attach"
tags: ["Customers"]
---

# Attach Documents to Business Customer V2

`POST /v2/customers/{customer_id}/business/attach`

Attach formation, ownership, and supporting documents to an existing business customer. Documents are categorised into three arrays: formation_documents, ownership_documents, and supporting_documents, replacing the v1 ownership_structure / company_details / legal_presence structure.

## Path parameters

- `customer_id` string, uuid, required

## Request body

- AttachDocumentsToBusinessCustomerV2Input
  - `formation_documents` V2FormationDocumentItem[] — Documents proving the legal existence of the business (e.g., Certificate of Incorporation, Articles of Incorporation, Trust Agreement, Tax registration certificate).
    - `type` 'REGISTRATION_DOCUMENT' | 'CONSTITUTIONAL_DOCUMENT' | 'FORMATION_DOCUMENT' | 'PROOF_OF_TAX_IDENTIFICATION' | 'EVIDENCE_OF_DIRECTORS_AND_CONTROLLERS' — Formation document type.
    - `description` string — Optional human-readable description of this specific document.
    - `files` object[], required — One or more file URIs obtained from [Upload Document](https://developer.fin.com/api-reference/customers/upload-document) endpoint.
      - `uri` string, required — File URI returned by the upload endpoint.
  - `ownership_documents` V2OwnershipDocumentItem[] — Documents proving who controls and owns the business (e.g., Shareholder Register, Org Chart, Power of Attorney, Directors Registry).
    - `type` 'OWNERSHIP_INFORMATION' | 'OWNERSHIP_CHART' | 'PROOF_OF_SIGNATORY_AUTHORITY' — Ownership document type.
    - `description` string — Optional human-readable description of this specific document.
    - `files` object[], required — One or more file URIs obtained from [Upload Document](https://developer.fin.com/api-reference/customers/upload-document) endpoint.
      - `uri` string, required — File URI returned by the upload endpoint.
  - `supporting_documents` V2SupportingDocumentItem[] — Additional compliance and operational documents (e.g., Proof of Address, Proof of Source of Funds, AML Comfort Letter, Marketing Materials).
    - `type` 'SHAREHOLDER_REGISTER' | 'PROOF_OF_NATURE_OF_BUSINESS' | 'PROOF_OF_ENTITY_NAME_CHANGE' | 'CERT_OF_INCUMBENCY' | 'PROOF_OF_SOURCE_OF_FUNDS' | 'PROOF_OF_SOURCE_OF_WEALTH' | 'AML_COMFORT_LETTER' | 'MARKETING_MATERIALS' | 'TAX_EXEMPT_ENTITY_CONFIRMATION' | 'E_SIGNATURE_CERTIFICATE' | 'FLOW_OF_FUNDS' | 'PROOF_OF_NATURE_OF_BUSINESS_LICENSE' | 'PROOF_OF_NATURE_OF_BUSINESS_AML_POLICY' | 'EVIDENCE_OF_GOOD_STANDING' | 'PROOF_OF_ACCOUNT_PURPOSE' | 'PROOF_OF_ADDRESS' | 'OTHER' — Supporting document type.
    - `description` string — Optional human-readable description of this specific document.
    - `files` object[], required — One or more file URIs obtained from [Upload Document](https://developer.fin.com/api-reference/customers/upload-document) endpoint.
      - `uri` string, required — File URI returned by the upload endpoint.
  - `tos_policies_value` string, required — Parsed from the tos_policies_value query parameter in the tos_policies_url returned by POST /v2/customers/business. Signifies the customer has accepted the Terms of Service.

## Response `200`

Documents attached successfully

- object
  - `data` object — Generic response object

## Other responses

- `400` — Validation failed
- `401` — Authentication failed due to invalid credentials
- `404` — Resource not found
- `422` — Failed due to a formatting error.

---

[API](https://skmtc.net/fin/apis/fin-com-api.md) · [All operations](https://skmtc.net/fin/apis/fin-com-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/fin/fin-com-api/revisions/6e69503ee7b8/schema)