Invoice Processing Tool – AP Automation with Human-in-the-Loop Invoice Review

An AI-assisted pipeline that reads invoices, matches vendors, and posts GST-compliant draft bills to Zoho Books under human approval.

Project Overview

Accounts payable work in India still runs largely on manual entry: read the invoice, retype it into the accounting system, apply the GST rules by hand. Formats vary, vendor names never quite match, and there is rarely a record of who touched what. Our client wanted that effort removed without giving up control over what reaches their books.

What We Did?

We designed the workflow around one decision: AI reads, a person approves. That boundary shaped the architecture. An OpenAI vision model extracts vendor details, line items, taxes, and dates from uploaded PDFs and images, and a reviewer confirms the result in a side-by-side interface before anything is published.

Vendor identification needed more than a name lookup, so we built a cascade that tries GSTIN first, then phone, then exact name, then fuzzy matching with RapidFuzz, and finally LLM disambiguation. An unmatched vendor is created at publish time. A second LLM pass picks the GL account from vendor and line-item context.

Every bill lands in Zoho Books as a draft with the original document attached, which keeps final posting in the client’s hands. Each published invoice is written to Google Sheets by year and month, so the finance team has an audit trail they can open without us.

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What  We Did?
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What Made the Project Successful?

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Full automation would have put unverified data into the client's books. Approval was placed at the end of every run, which made the AI useful without making it the final authority.

Tech Stack

Language: Python 3.12 Framework: FastAPI (0.136.0) with Starlette Server: Uvicorn Validation & Configuration: Pydantic (v2.x), pydantic-settings, python-dotenv Authentication & Security: python-jose (JWT with HS256), Google ID-token verification, middleware for request tracking, audit logging, and error handling File Upload Handling: python-multipart

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