# DuplicateBillAlert

> Blocking. Duplicate payment is the most common AP loss.

Source: https://lopifi.com/components/duplicate-bill-alert
Part of: Lopifi — US GAAP books on autopilot, reviewed by a CPA (https://lopifi.com)

---

- **Family:** Payables (AP) — 
- **Status:** Implemented
- **Spec:** https://lopifi.com/docs/catalog/11-payables

## Install

```bash
npx shadcn@latest add @lopifi/theme
npx shadcn@latest add @lopifi/duplicate-bill-alert
```

## Specification

> **Duplicate payment is one of the most common — and most preventable — AP losses.**

Runs before save. Primary key: `vendor + vendorInvoiceNumber`. Secondary fuzzy check: `vendor + amount + date ± 5 days`. **Blocking**, showing the suspected duplicate side by side with the new entry. Also detects duplicate *vendors* by name similarity and tax ID — duplicate vendors are how duplicate payments survive duplicate-invoice checks.

## Rules this component obeys

Money is minor units, never floats. `null` is not `0` and neither is redacted. Negatives render in accounting parentheses with the parenthesis column reserved on both sides. Debit and credit are two columns. Per-currency decimal places. Polarity is explicit — up is not always good. Every figure states its period, entity, currency, basis and as-of.