Close the Month Before Your Accountant Does

What this does

If you run an online store, month-end means matching card payments to your books and working out what you earned. Most owners do it by hand, and mistakes sit in the books until an accountant finds them.

Anthropic's Small Business plugin for Claude can take that job on. Three of its skills cover the month-end work.

• month-end-prep checks your card payouts against your books and lists duplicate charges, uncategorized transactions and missing receipts. Then it writes a plain-English summary of what you earned and spent.
• report-builder packages the month for your accountant as a chat summary and an Excel file, and saves the report so you can run it again next month.
• tax-season-organizer works out your estimated quarterly tax and shows its assumptions. It also lists the contractors you paid and flags any who have not sent you a W-9, the form with their tax details.

You decide on every flagged item. The plugin never fixes one on its own.

Completion test: you have a close packet (an Excel file and a one-page PDF), a report for your accountant, and a list of anything still open with your decision beside it. If a flag has no decision, the close is not finished.

What you need

Install it.

1. Open the Claude desktop app and click Customize in the left sidebar.
2. Under Plugins, click +.
3. Find Small Business and click Install.
4. Say "get me started" to run its setup, which learns your business and offers to connect tools. You can skip connecting anything. Anthropic's README says every skill still works from a CSV export.

Anthropic's install guide is linked in section 9 if your screen looks different.

What it costs. The plugin's code is under the Apache-2.0 licence, so installing it is free. It runs inside Claude, so you still need the paid Claude plan.

Step 1: close the month

Upload your three files, then send:

/close-month

That short version is enough to start. For a fuller start, paste the detailed version below instead and replace the part in square brackets. It answers the plugin's usual opening questions up front, so there are fewer back-and-forths.

/close-month

Close the books for [month and year, for example October 2026]. I run an online store in the United States. The books are still open and nothing has been filed. Nothing is connected, so use the three files I uploaded: the profit and loss report, the transaction detail, and the card payout report.

For receipts, the "Attachment count" column in the transaction detail shows which expenses have a receipt attached.

Check my card payouts against my books. List every uncategorized transaction, every possible duplicate charge, every card payout that is missing from my books, and every expense with no receipt. For each one, show the name, the date and the amount, and wait for my decision.

Don't change anything in my books. I will make every change myself. When every flag has a decision, ask me before you write the summary and export the close packet. Don't send anything to anyone.

The plugin still pauses at every gate, so you approve each flag and sign off yourself. Add this line to the end if you only want the close and not the cash forecast: "Stop after the close packet and skip the cash forecast."

The plugin works through a checklist and stops at each gate for your answer. The questions come in roughly this order. The right-hand column shows how the sample store answered.

Good to know.

• The plugin will not move past open uncategorized items unless you answer them or say "skip for now".
• It never changes or voids anything in your books. You make those changes yourself.
• After the summary, /close-month goes on to offer a refreshed cash forecast and a published packet. It asks before each, and it will not send anything to your accountant until you approve the message.

What you get. A plain-English summary of the month (about 150 to 250 words) and a close packet. The packet is an Excel file with the profit and loss, the reconciliation and an Action Items sheet for anything still open, plus a one-page PDF summary.

Step 2: build the report for your accountant

In the same chat, send:

Build me a report for my accountant: revenue, cost of goods, gross margin and net income compared with the month before, plus expenses by category.

For a fuller version that answers the plugin's questions up front, paste this instead and replace the part in square brackets:

Build me a report for my accountant for [month and year]. Use the profit and loss file I uploaded.

Show revenue, cost of goods sold, gross profit, gross margin percent, operating expenses by category, and net income. Compare each number with the month before and show the change in dollars and in percent. Call out any expense category that moved by more than 10%.

Use the calendar month. If my books still have flagged items open, such as uncategorized transactions, duplicate charges or missing payouts, list them at the top of the report so my accountant knows.

Give me a short summary in the chat first, with the biggest changes at the top. Then build an Excel workbook with a summary tab first and the raw numbers on the last tab, so I can check the math. Save this report so I can run it again next month. If a number is missing or looks wrong, tell me instead of guessing.

The report-builder skill asks which period the report covers, such as a calendar month, the last 30 days or month-to-date. It then shows you its plan once and waits for a yes. Example answer: "Calendar month. Yes, go ahead."

What you get. A chat summary first, with each number next to its comparison with the month before. Then an Excel workbook with a summary tab first and your raw data on the last tab, so you can check the math. You also get a page version of the same report.

The skill saves the report, so next month you can say "same report as last time."

Step 3: estimated taxes and contractor W-9s

Open a new chat, upload your year-to-date profit and loss and your contractor payments file, and send:

/tax-prep

For a fuller start, paste this instead and replace the parts in square brackets. It answers the plugin's usual questions up front:

/tax-prep

Prepare both my estimated quarterly tax and my contractor list. I run an online store in the United States. I am a sole proprietor and I file as single. Use the year-to-date profit and loss and the contractor payments file I uploaded.

My books are closed and reconciled through [last closed date, for example September 30]. The year runs evenly, so annualize my profit. I have paid [amount] in estimated tax so far this year, in [number of payments and amounts].

Use the current tax year's figures. If you only have figures for another year, tell me which year they are, then look up the current ones on IRS.gov or ask me. State every assumption.

For contractors, list everyone I paid, show who has a W-9 on file and who is missing one, and flag anyone paid through PayPal. Don't file anything. This is prep material for my accountant.

What you get.

• The estimate. Your quarterly payment with its due date, and a full list of assumptions: business type, the tax rate assumed and what was left out. The plugin's default is a flat 22% rate, and it leaves out deductions such as the QBI deduction (a deduction for pass-through business income) and state taxes.
• The contractor list. Everyone you paid for services, who has a W-9 on file, and an action list of who is missing one. It flags anyone paid through PayPal or Stripe, because the processor may report those payments itself.
• A header on every page that says it is prepared for review by your accountant and is not tax advice.

Check the tax year. The plugin's built-in tax figures are for 2025. For any other year it says so, then asks you for current numbers or looks them up on IRS.gov. Read the year in the page header before you use a number.

What the example store's books contain

The example is Pinecrest Home Goods, an invented online store, with its October 2026 books. Four things were planted for the check to find.

Why it matters. As booked, October shows a net loss of $3,273.35. The missing payout and the duplicate charge together are worth $8,873.70. With both fixed, the month is a profit of $5,600.35. We worked that out by hand from the example files. A month that looks like a loss turns out to be a profit.

The contractor file. It lists payments to five contractors this year, through October 31. Hollis Photo Studio ($7,850) and Tyler Brooks ($5,400) have a W-9 on file. Marisol Reyes ($4,250), Jenna Whitfield ($3,200) and Ben Alvarez ($520) do not. Jenna is paid through PayPal.

Check it before you rely on it

• Open three flagged items in your own accounting app and confirm each one is real. Anthropic's own tutorial suggests checking one line against something you already know.
• Make every change yourself in your accounting app. The plugin only flags. It never edits your books.
• Compare the revenue, margin and net income in the summary with your profit and loss file.
• Treat the tax figure as a draft. Read the assumptions list and send it to your accountant with the packet.
• Check the tax year in the page header before you use any number.

Pass: the flags are real, the summary's figures match your file, and every assumption on the tax page is one your accountant can accept.

Stop: a flag you cannot find in your books, a total that does not match your file, or a tax page that does not say which year its figures are for.

Honest limits

• The plugin changes between versions. This guide follows version 1.35.1 (September 15, 2026). Anthropic's pages describe different versions: one says 15 skills and the version this guide follows says 44. Do not rely on a count.
• It is not advice. Anthropic says the plugin does not provide financial, tax, legal or HR advice. Everything it produces is for you and your accountant to review.
• The tax math is US federal only, with a default flat 22% rate, no deductions applied and state taxes left out.
• The contractor line may be out of date. The plugin's skill file tests contractors against $600. For payments made after December 31, 2025, the federal reporting threshold for Form 1099-NEC is $2,000. Payments made through PayPal or a card may be reported by the processor on Form 1099-K instead, which is why the plugin flags them. Ask your accountant which rules apply to you.
• It needs the Claude desktop app and a paid Claude plan.
• The example is invented. The store, its books and its contractors were written for this guide.

How this guide was made. This guide was not run end to end by its writer. It follows the published skill files for month-end-prep, report-builder, tax-season-organizer, close-month and tax-prep (version 1.35.1), and Anthropic's install guide. Sources were checked on November 6, 2026. Steps and wording on your screen may differ.

Links

• Small Business plugin on the Claude marketplace
• How to install and use the Claude for Small Business plugin (Claude Academy)
• Using Claude for your small business: the month-end walkthrough (Claude Academy)
• Small Business plugin source, version 1.35.1
• Anthropic's repository of plugins (Apache-2.0)
• Introducing Claude for Small Business (Anthropic)
• Form 1099 filing changes under the new $2,000 threshold (NATP)