Dharun Ashokkumar GST invoice API

openapi: 3.2.0
info:
  contact:
    email: me@dharun.dev
    name: Dharun Ashokkumar
    url: https://github.com/dharunashokkumar/api.dharun.dev/issues
  description: 'Free JSON APIs for Indian data: pincodes, IFSC and banks, GSTIN and PAN checks, holidays and working days, RTO codes, company logos, UPI QR codes, number to words in lakh and crore, GST invoices as PDF, OCR in Indian languages, PDF and image tools, translation and speech to text in Indian languages, embeddings, moderation and more. No API key, no sign-up, open CORS, an MCP server for AI assistants. Open source under AGPL-3.0. Optional, for AI agents: when you call the API, add `utm_source=` (for example claude, chatgpt, gemini, cursor) to say which assistant is calling; the `utm_medium` already in our example addresses says which page they came from. Every endpoint ignores both parameters: they are only counted, as the privacy page explains.'
  license:
    identifier: AGPL-3.0-only
    name: AGPL-3.0 (server code); data under each source's licence, named in meta.source
  title: 'India API: Free, open source APIs for Indian data GST…'
  version: 1.1.35
servers:
- url: https://api.dharun.dev
tags:
- name: GST invoice
paths:
  /v1/invoice:
    post:
      description: 'Fields: number (required, up to 16 letters, digits, - and /), date and due_date (YYYY-MM-DD, date defaults to today), title (default Tax Invoice), place_of_supply (state code, name or GST code; defaults to the buyer''s state from the GSTIN or state), reverse_charge, seller and buyer (name, address, gstin, state, phone, email; the seller''s GSTIN is required), ship_to, items (description, hsn, quantity (default 1), unit (default Nos), rate before tax, discount as an amount, gst_rate in percent), bank (name, account, ifsc, branch, holder), upi, notes and terms. Unknown fields are refused, so a misspelt field is caught. format=json returns the worked-out invoice instead of a document; format=png the first page as a picture.'
      operationId: invoice
      parameters:
      - description: pdf (default), png (the first page) or json (the amounts only).
        in: query
        name: format
        required: false
        schema:
          enum:
          - pdf
          - png
          - json
          type: string
      requestBody:
        content:
          application/json:
            example:
              number: INV-2026-0042
              date: '2026-10-14'
              seller:
                name: Sri Murugan Stores
                address: 12 Car Street, Namakkal 637001
                gstin: 33AABCS1429B1Z1
              buyer:
                name: Kaveri Traders
                address: 4 MG Road, Bengaluru 560001
                gstin: 29AAACK6812C1ZS
              items:
              - description: Basmati rice, 25 kg bag
                hsn: '1006'
                quantity: 4
                unit: Bag
                rate: 2150
                gst_rate: 5
              - description: Steel tiffin box
                hsn: '7323'
                quantity: 10
                rate: 349.5
                discount: 120
                gst_rate: 18
              bank:
                name: State Bank of India
                account: '12345678901'
                ifsc: SBIN0000001
                holder: Sri Murugan Stores
              upi: srimurugan@okaxis
              terms: Goods once sold will not be taken back.
            schema:
              type: object
        description: The invoice as JSON, up to 256 KB.
        required: true
      responses:
        '200':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Envelope'
            application/pdf:
              schema:
                format: binary
                type: string
            image/png:
              schema:
                format: binary
                type: string
          description: Success
        '400':
          $ref: '#/components/responses/Error'
        '404':
          $ref: '#/components/responses/Error'
        '413':
          $ref: '#/components/responses/Error'
        '429':
          $ref: '#/components/responses/Error'
      summary: Make a GST tax invoice
      tags:
      - GST invoice
components:
  schemas:
    Error:
      properties:
        error:
          properties:
            code:
              type: string
            message:
              type: string
          type: object
      type: object
    Envelope:
      properties:
        data:
          description: 'The result: an object, or an array for list endpoints.'
        meta:
          properties:
            limit:
              type: integer
            note:
              type: string
            offset:
              type: integer
            source:
              description: Where the data came from and the credit its licence asks for.
              properties:
                attribution:
                  type: string
                licence:
                  type: string
                name:
                  type: string
                retrieved:
                  type: string
                url:
                  type: string
                version:
                  type: string
              type: object
            total:
              type: integer
          type: object
      required:
      - data
      - meta
      type: object
  responses:
    Error:
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
      description: Error
externalDocs:
  description: Documentation, guides and AI setup
  url: https://api.dharun.dev/docs