---
name: why-did-margin-change
description: "Use when the user has a RoboLedger connection and asks why gross margin moved, and wants the change traced to the accounts and transactions behind it from the live ledger. Triggers: why did margin drop, margin change, gross margin analysis, what drove the variance."
---

# Ask your books why gross margin changed

Trace a margin change to the accounts and transactions behind it, from a live ledger, without exporting anything.

## When to use it

When the number moved and the first question is why. In a plain chat you'd export a trial balance and paste it. Connected to the ledger, the assistant reads statements, accounts and the transactions underneath them directly, as of your last sync, so it can keep going down a level until the answer is a list of entries you can check.

**Setup.** This needs your books connected through RoboLedger: [Connect your books to your AI assistant](https://roboledger.ai/docs/connect-your-books). It works in Claude, ChatGPT or any MCP client. Asking questions never writes to QuickBooks. What the assistant can read is in [Ask about your books](https://roboledger.ai/docs/ask-about-your-books).

**Where it works.** Needs your books connected to your AI assistant through RoboLedger.

## Ask the user for

- The two periods to compare.
- Whether you want live figures or the closed month. For something you’ll show someone, use closed months.

Ask for anything missing before you start. Never invent a figure to fill a gap.

## Do this

Carry out the request below. Fill each [bracketed] item from what the user gave you.

Gross margin moved between [period A] and [period B]. Find out why.

1. Check that the books are current first, and tell me when they last synced.
2. Show revenue, cost of revenue and gross margin for both periods. Tell me whether you're using live figures or the closed month.
3. Break the change into its parts: how much came from revenue volume, how much from a change in the mix of what we sold, and how much from cost of revenue per unit of revenue. Show the arithmetic.
4. Go down to the accounts that moved most, and then to the largest transactions in each.
5. Tell me anything that looks like a one-off or a misclassification, such as a cost posted to the wrong account or a revenue entry in the wrong month.

Don't change anything in the books. List the entries I should look at, with dates and amounts.

## Before you hand it over

Tell the user which of these checks they still need to make:

- Open the listed entries and confirm what they are before drawing a conclusion.
- If a misclassification is suggested, fix it in the books through your normal process, not from the chat.
- Before sharing any figure, confirm whether it came from live books or a closed month.

The assistant drafts. The person whose name is on the work approves it.

## What a good answer looks like

*Illustrative figures for a made-up company.*

Books last synced today at 9:14. Using closed months.

**Gross margin** fell from 44.2% in July to 39.8% in August.

- Revenue rose $18,400, to $212,600.
- Cost of revenue rose $19,600, to $128,000.

**What moved it**
1. **Mix (−2.9 points).** Installation revenue, the lower-margin line, went from 31% of revenue to 42%.
2. **Subcontractor cost (−1.5 points).** Account 5120 rose $9,600. Two entries account for $8,100:
   - 08-12, Northfield Electrical, $4,700
   - 08-26, Northfield Electrical, $3,400

**Worth a look.** The 08-26 entry's memo references a July job. If the work was done in July, it may belong in July's cost of revenue.

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From the Harbinger FinLab skill library: https://harbinger.finance/skills/why-did-margin-change