Mistake to Avoid: Letting AI Invent Expense Categories
A visual tip for bookkeepers: give an AI agent a fixed list of categories plus Needs Review, so it never makes up a category name.
The guide in text
The mistake
Letting the AI invent categories
A plain chatbot will happily make up a category name, and Misc Business Stuff ends up in the books.
Do this instead
Give it a fixed list plus Needs Review. If a charge is unclear, it picks Needs Review and says why.
The full definition: What is expense categorization? in the AI glossary, with an example from a free lesson, common confusions and tips.
Businesses and people in the examples are made up. The steps, screens and wording come from the free lesson and the Stepthrough glossary and prompt library.
Do it yourself, free
Build an AI Agent That Categorizes Business Expenses. Build an AI agent for Maple Street Bookkeeping that sorts business expenses into categories, writes a short note for each and saves them to Google Sheets — chat trigger, AI Agent, system prompt… You do every step yourself in a practice copy of n8n, it checks your work as you go, and “Do it for me” finishes any step you get stuck on. Free, and nothing touches your real accounts.
Start the free lessonRelated terms
Plain-English definitions, each with an example from a free lesson.
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From the blog
How to Stop ChatGPT from Making Things Up: 5 GuardrailsStop ChatGPT from making things up with five guardrails: a facts list, a Not stated rule, never-invent rules, a closed category list and a final check.
Oct 1, 2026 6 min read
Automate Expense Reimbursement Requests with AIExpense reimbursement automation for small teams: a Lovable form and an n8n AI agent that checks the policy, logs it in Sheets and emails the status.
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Get Receipts into Google Sheets with AI and n8nReceipts to Google Sheets without typing: build an n8n agent that reads a receipt photo, picks a category and adds a row. Plus an expense categorizer.
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More visual guides
5 Steps to an AI Agent That Categorizes Business ExpensesA visual guide: an n8n agent sorts expenses into a fixed list of categories, flags unclear ones as Needs Review and saves them to Google Sheets.
Step-by-step guide 7 slides
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Mistake to Avoid: Not Setting a Length in Your PromptA visual tip: say the length in the Format part of your prompt, like under 120 words, instead of trimming a 300-word reply by hand.
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