Expense Categorization

---
title: "Expense Categorization"
description: "Classify business expenses into the correct Chart of Accounts categories, handle split transactions, manage recurring entries, and apply consistent categorization rules. Use when asked to categorize expenses, sort transactions into tax categories, map receipts to COA codes, or clean up miscategorized entries."
author: AgentArmory
license: Proprietary
---

# Expense Categorization

Classify business expenses into the correct Chart of Accounts (COA) categories using a combination of rules-based mapping, contextual analysis, and structured exception handling. Covers COA mapping strategies, multi-category split transactions, recurring entry patterns, and five documented agent classification failure modes.

Expense categorization is the most frequent bookkeeping action in small-business accounting (Ramp, 2025), yet AI expense classification systems produce **15-25% miscategorization rates** on non-English vendor descriptions and ambiguous transaction types (Navan internal audit, 2026). This skill counteracts the patterns that produce miscategorization through a four-phase methodology with explicit guardrails.

This skill is a focused deep-dive complementing the categorization step in Phase 2 of **Personal Bookkeeping & Ledger Management** (linked-topic-personal-productivity). Use this skill when the task IS expense categorization; use the parent skill when the task is broader bookkeeping that includes categorization as part of a larger recording workflow.

---

## When to Use

Use when someone asks to categorize expenses, sort transactions, map expenses to tax categories, clean up bad categorizations, handle recurring bills, split a transaction across categories, or reconcile expense categories between periods. Also when the user provides a list of transactions or receipts and needs them properly classified.

## Triggers

"categorize these expenses", "sort these transactions", "classify this receipt", "which category does this go in", "COA mapping", "split this transaction", "recurring expense", "subscription categorization", "miscategorized expenses", "fix expense categories", "clean up my categories", "expense classification rules", "tax category mapping", "GL code", "general ledger code", "accounting categories"

## Methodology

### Phase 1: Establish the Category Framework

#### Step 1.1: Understand the Business Type

Before categorizing a single transaction, determine the business type because different businesses have different standard expense structures:

- **Service business (consulting, agency, freelancer):** Professional fees, software subscriptions, marketing, travel, office supplies dominate.
- **Product business (retail, e-commerce, manufacturing):** COGS (cost of goods sold), inventory, shipping, warehousing, raw materials, fulfillment dominate.
- **Mixed business (SaaS, marketplace):** COGS (hosting, API costs) + service expenses (sales, marketing, R&D).
- **Nonprofit:** Program expenses, fundraising, administrative/management, grant-specific costs.

**Decision rule:** If the business type is not stated explicitly, infer it from the user's description of their work, the mix of transactions, or ask. Default to service business classification for freelancers/solopreneurs.

#### Step 1.2: Load or Create the COA Mapping Table

If a COA already exists (from Personal Bookkeeping & Ledger Management or direct user input), load it. If not, create a mapping table with these columns:

```
| Category Keyword | COA Account | Default? | Split Rule | Tax Relevance |
|-----------------|-------------|----------|------------|--------------|
```

**Default mapping table (service business, standard):**