Small Businesses Lose $1.5B/Year to Duplicate Payments. Catch Them in 5 Minutes

Your AP clerk is paying the same invoice twice and nobody knows.

That's not hypothetical. Duplicate payments are one of the quietest cash leaks in small business — the same invoice gets keyed in twice, two departments both pay the vendor, or a recurring charge is never cancelled after the first payment. American businesses lose an estimated $1.5B+ a year to duplicate payments alone. And the other half of the problem is the opposite: invoices that sit overdue for 90+ days because nobody is watching the aging report.

Here's the thing: QuickBooks and NetSuite both have aging reports. But pulling them out, mapping columns, and actually reviewing 200 rows of payables every week? Nobody does that. Excel formulas rot. The "accounting person" is usually the owner wearing a third hat.

So I built a local, zero-dependency tool that turns a boring CSV export into an AP watchdog in one command.

What it does:

• Aging analysis — buckets every unpaid invoice into current / 1-30 / 31-60 / 61-90 / 90+ with amounts summed per bucket
• Overdue alerts — lists every late invoice sorted by days overdue, and exits with code 1 so you can hook it into cron/CI and get alerted daily
• Duplicate detection — flags invoices from the same supplier with the same amount within 14 days as suspicious duplicates, with the risk amount shown
• Cash flow view — sums what's due in the next 30 / 60 / 90 days so a payment wall never sneaks up on you
• Paid-invoice exclusion — already-paid rows (paid/closed/settled/已付) are automatically skipped
• Markdown + JSON reports, filtering by supplier or min amount, and it's 100% local — your data never leaves your machine

It auto-detects Chinese column headers too (供应商/发票号/金额/开票日期), which is a nice surprise if your books are bilingual.

The exit-code contract is the real feature. Run it daily in cron:

0 8 * * * python3 ap_checker.py --csv payables.csv

Code 0 = clean. Code 1 = overdue or duplicate found (your cron fires an alert). Code 2 = bad input. You get a daily AP security guard for free, forever, with no SaaS subscription and no data upload.

Built with Python stdlib only (csv/argparse/json/datetime/collections) — no pip install, no dependencies, Python 3.8+. One-time purchase, free updates, instant download.

If you run a small business, do bookkeeping for clients, or just want to stop paying vendors twice, grab it here: agentechip.com — it's in the store along with the rest of the financial toolkit (invoice cleanup, cash flow forecasting, consignment tracking).

Your AP ledger is bleeding. It takes 5 minutes to find out.