> ## Documentation Index > Fetch the complete documentation index at: https://developer.sandbox.co.in/llms.txt > Use this file to discover all available pages before exploring further. # Generate OTP > Generate OTP to authenticate tax payer. **Prerequisites:** You must enable API access to get access to GST APIs. If not done already, [enable API access](/api-reference/gst/compliance/guides/taxpayer/authentication/enable_api_access). ## OpenAPI ````yaml api-reference/gst/compliance/openapi.json POST /gst/compliance/tax-payer/otp openapi: 3.0.1 info: title: compliance description: >- **GST Compliance API** enables businesses to automate compliance requirements like [Taxpayer verification](https://developer.sandbox.co.in/reference/search-gstin-api), [GSTR Filing](https://developer.sandbox.co.in/reference/gst-taxpayer-authentication), [Generating E-Invoices](https://developer.sandbox.co.in/reference/e-invoice-authentication-api), and [E-Way Bills](https://developer.sandbox.co.in/reference/e-way-bill-authentication-api).We provide these APIs from GSTN-authorised GST Suvidha Providers, handling the encryption-decryption and signing so you don't have to handle the complexities. version: 1.0.0 servers: - url: https://api.sandbox.co.in - url: https://test-api.sandbox.co.in security: [] tags: - name: Public - name: Taxpayer - name: Taxpayer Auth - name: Returns - name: GSTR-1 Documents - name: File GSTR-1 - name: GSTR-2A Documents - name: GSTR-2B Document - name: File GSTR-3B - name: GSTR-4 - name: File GSTR-9 - name: Invoice Management System - name: GSTR-1A Documents - name: File GSTR-1A - name: Ledgers - name: e-Invoice - name: Sales e-Invoices for return period - name: Purchase e-Invoices for return period - name: Front Office Notices - name: Front Office - name: AATO - name: e-Invoice1 - name: Authentication - name: e-Invoice12 - name: E-Way Bill - name: E-Way Bill1 - name: Authentication1 - name: Consignor - name: Consolidated E-Way Bill - name: Multi-Vehicle Movement - name: Consignee - name: Transporter - name: Consolidated E-Way Bill1 - name: Multi-vehicle Movement - name: Common paths: /gst/compliance/tax-payer/otp: post: tags: - Taxpayer - Taxpayer Auth summary: Generate OTP description: Generate OTP to authenticate tax payer. operationId: generateOtp parameters: - name: authorization in: header description: JWT access token required: true example: '{{access_token}}' schema: type: string - name: x-source in: header description: 'Source. Possible Values: primary (default) or secondary' required: false example: primary schema: type: string default: primary example: primary - name: x-api-key in: header description: API key for identification required: true example: '{{api_key}}' schema: type: string - name: x-api-version in: header description: API version required: false example: '' schema: type: string default: 1.0.0 requestBody: content: application/json: schema: type: object required: - username - gstin properties: username: type: string description: Username as per GST portal gstin: type: string description: GSTIN of the taxpayer examples: 200 Success: value: username: TN_NT2.2477 gstin: 33ABKCS2033B1ZW summary: 200 Success TEC4001 OTP generation failed: value: username: globex.edu.co gstin: 23ABCCQ2000E000 summary: TEC4001 OTP generation failed AUTH403 Maximum sessions reached: value: username: acme.gj.com gstin: 24AAACQ3770E000 summary: AUTH403 Maximum sessions reached responses: '200': description: >- 200 Success / TEC4001 OTP generation failed / AUTH403 Maximum sessions reached content: application/json: schema: type: object properties: code: type: number example: 200 data: type: object properties: error: type: object properties: error_cd: type: string example: TEC4001 message: type: string example: >- OTP generation failed as OTP server is down. Contact Support status_cd: type: string example: '1' timestamp: type: number example: 1712926086000 transaction_id: type: string example: 9a6ce7b9-de63-48a8-b45b-0c5420538b25 examples: 200 Success: summary: 200 Success value: code: 200 data: status_cd: '1' timestamp: 1712926086000 transaction_id: 9a6ce7b9-de63-48a8-b45b-0c5420538b25 AUTH403 Maximum sessions reached: summary: AUTH403 Maximum sessions reached value: code: 200 data: error: error_cd: AUTH403 message: >- Maximum session allowed for user with this GSP account exceeded. status_cd: '0' timestamp: 1763446641000 transaction_id: 7047f26a-0993-4cab-8e7c-553034d3a3b4 TEC4001 OTP generation failed: summary: TEC4001 OTP generation failed value: code: 200 data: error: error_cd: TEC4001 message: >- OTP generation failed as OTP server is down. Contact Support status_cd: '0' timestamp: 1763446641000 transaction_id: c0cba77f-4942-49f5-8a18-6c62d69f354b headers: {} '422': description: Invalid GSTIN Pattern content: application/json: schema: type: object properties: code: type: number example: 422 message: type: string example: Invalid GSTIN pattern timestamp: type: number example: 1763446641000 transaction_id: type: string example: 021ff404-5b8b-468b-ab92-68ff5a54590b examples: Invalid GSTIN Pattern: summary: Invalid GSTIN Pattern value: code: 422 message: Invalid GSTIN pattern timestamp: 1763446641000 transaction_id: 021ff404-5b8b-468b-ab92-68ff5a54590b headers: {} deprecated: false security: [] ````