RAG vs ChatGPT for Business Documents: What Works

A managing director at an 80-person accounting firm types a question into ChatGPT: "What are the updated DATEV posting rules for travel expense invoices?" ChatGPT gives a confident, well-formatted answer — based on training data from 2023. The relevant DATEV update happened in 2024. Nobody catches it until the quarterly review.

RAG and ChatGPT are not interchangeable tools doing the same job. They have fundamentally different architectures. That difference is irrelevant until the moment you need answers from your own documents — and then it is the only thing that matters.

How Retrieval Augmented Generation Works for Business Data

RAG — Retrieval Augmented Generation — is a technical architecture, not a product name. Before the AI generates any answer, it searches your documents first.

When you upload a file, it gets split into chunks — typically 400 to 800 tokens each. Each chunk is converted into a vector: a list of 1,024 numbers that represents its meaning in mathematical space. We use Mistral Embed for this, which produces 1,024-dimensional embeddings. Those vectors are stored in PostgreSQL with the pgvector extension, indexed with HNSW (Hierarchical Navigable Small World) indexing — chosen because it works on empty tables from day one and has better recall than IVFFlat.

When you ask a question, that question also becomes a 1,024-dimensional vector. The system finds the chunks whose vectors are closest to your question by cosine similarity and feeds those chunks to the language model. The LLM generates an answer based only on what those chunks contain. Every answer includes a citation: which document, which page.

The model never invents. It summarizes what it found.

ChatGPT Company Documents: Three Problems That Don't Go Away

ChatGPT is capable across many tasks. Working with your internal documents is not one of them — and the reasons are structural, not something a plugin fixes.

It cannot see your files. ChatGPT's knowledge comes from public data scraped before its training cutoff. Your NDAs, process manuals, client contracts — ChatGPT has never seen them. You can paste text into a prompt, but that has a context length limit, puts data into OpenAI's systems, and requires a human to do the pasting every single time.

It hallucinates without source data. When ChatGPT does not know something, it fills the gap with plausible-sounding text. In a consumer context, this is a nuisance. In a business context — tax advice, HR policy, contract interpretation — it is a liability.

Knowledge cutoff. Your industry's updated regulations, your clients' changed profiles, your process documents from last month — none of that exists in a general-purpose model's training data. For AI document search that reflects the current state of your business, you need a system connected to your actual documents.

RAG vs ChatGPT for Business Use: A Direct Comparison

| | RAG System | ChatGPT | |---|---|---| | Accesses your internal documents | Yes | No | | Answers from current data | Yes — documents updated in real time | No — knowledge cutoff applies | | Source citations | Yes — document name and page | No | | Hallucinates | Rare — bounded by retrieved content | Common without source grounding | | GDPR data residency | Yes — data stays in EU | Requires careful configuration | | Per-client data isolation | Yes — separate schema per client | No concept of this |

The table makes it look simple. But the compliance column is where most companies underestimate the problem.

Why the Technical Architecture Matters for GDPR

Many mid-market companies assume the compliance question is answered when they add a plugin that "connects ChatGPT to their documents." It is not.

Your documents are being sent to US servers and processed by a model that may use them for training unless you have opted out and can prove it.

With a properly built RAG system, the architecture itself handles the compliance:

• Documents stored in PostgreSQL on Hetzner servers in Germany
• Per-client schema isolation — your data is never mixed with another company's data in the database
• Embeddings generated by Mistral Embed, a European AI provider
• LLM inference via Mistral AI, hosted in France, under EU data protection law
• No data crosses the EU boundary, by design rather than by policy

A policy document saying "we do not send your data outside the EU" is weaker than an architecture where there is no pathway for data to leave in the first place. That distinction matters to a DPO.

Two Cases Where This Changes Daily Operations

A tax advisory firm running 200 active client files can query any regulation, any past ruling, or any internal process note and get an answer with a source citation in under 3 seconds. New documents are searchable within minutes of upload. The associates stopped maintaining a shared spreadsheet of "which partner knows which client's history" — the system answers faster than anyone on the team.

A 60-person manufacturing company gave every department head access to their quality management documentation. When a production supervisor needs the non-conformance procedure at 7 AM on a Saturday, the answer does not depend on the QM manager being reachable. But it also does not depend on that procedure being written down clearly, which brings us to the real constraint.

RAG is only as good as the documents you feed it. If your processes exist in people's heads and not on paper, no amount of vector indexing will help. We have seen companies with sophisticated technical setups hit a wall because their documentation was three years out of date and nobody owned it. The technical deployment takes days. Getting your team to write things down — and keep writing them down — takes longer. That is the harder problem, and it is yours to solve.

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Curious how a RAG system handles your specific document types? Book a 30-minute demo — bring a PDF of your standard operating procedures, your HR handbook, or whatever your team most often needs to search. We will run it live and show you exactly what retrieval looks like on your actual content.