# An inventory management system that matches what's actually on the shelf Canonical: https://erpfly.com/modules/inventory-management/ Last updated: September 3, 2026 Category: Operations Your stock report says 70 units. The shelf says 52, and the buyer has started keeping her own list in a notebook. An inventory management system only helps if people believe it, so describe how your stock really moves and erpfly writes the ERPNext app or Odoo addon that enforces it. ### Features - **Reorder points from real usage.** Minimums calculated from recent issues and supplier lead time, per item and per warehouse. The job proposes a request. A person still decides to buy. - **Batch and expiry rules by item group.** Food, chemicals and pharma items must carry a batch and an expiry date. Hardware doesn't. The rule sits on the item group, so it isn't set item by item. - **Adjustments that need a reason.** Stock corrections go through the ledger with a reason code. Anything above a value you set waits for the operations manager before it posts. - **Projected stock you can explain.** A report that shows on-hand, reserved, ordered and projected quantity per warehouse, with a link to the transaction behind every number. - **Clean opening balances.** An import that loads items, warehouses and counted quantities in one dated posting, so your opening stock value is right on day one. ### What gets generated **ERPNext / Frappe app:** - Reorder Rule DocType (item, warehouse, lead time, safety days) - Nightly job in hooks.py scheduler_events raising Material Requests - doc_events validation on Stock Entry and Stock Reconciliation - Custom fields on Item and Item Group as fixtures - Projected stock Script Report built on Bin **Odoo addon:** - stock.warehouse.orderpoint inheritance with usage-based minimums - Reason codes on stock.quant inventory adjustments - @api.constrains on stock.lot for mandatory expiry dates - ir.cron job for the reorder calculation - Inherited list and pivot views on stock.quant ### Stock numbers the buyers stopped trusting Most inventory problems start as a habit, not a bug. A technician grabs three boxes of filters for a job and promises to sort the paperwork later. Now the system is wrong by three boxes. Give that a year and you've got a stock report the warehouse lead openly laughs at. ERPNext and Odoo both track stock properly out of the box. Every movement becomes a ledger entry, valuation follows FIFO or moving average, and batches and serial numbers are standard. What neither can do is guess your rules. Which items need a batch? Who may adjust stock without a count? When does a low quantity turn into a purchase request, and for how much? Those answers are yours, and they're the part erpfly writes. ### What goes into the inventory management system we generate On **ERPNext**, you get a Frappe app that sits beside ERPNext and never edits it. Typical pieces: custom fields on Item and Item Group shipped as fixtures, a small DocType for your reorder rules, `doc_events` in `hooks.py` that check Stock Entries before they post, and a Script Report that reads projected quantity from the Bin table. Nightly work goes into `scheduler_events`, so anyone can see what runs and when. On **Odoo**, it's an addon that extends `stock.quant`, `stock.move` and `stock.warehouse.orderpoint` through `_inherit`, with views that inherit the standard ones and access rights in `ir.model.access.csv`. Inventory itself is part of Community, so none of this needs Enterprise. One caveat. Both platforms already do fixed min/max reordering. If a fixed minimum works for an item, keep it. ### Worked example: a spare parts distributor outgrows fixed minimums Picture a distributor with about 4,000 SKUs of bearings, belts and seals across two warehouses. Fixed reorder levels were fine when the range was small. Now half of them are stale. Fast movers run out, slow movers sit for a year. The buyer, Leena, already has a rule. It just lives in her head: - Take the last 60 days of issues for each item in each warehouse, divided by 60, as daily use. - Reorder point is daily use times (supplier lead time + 7 safety days). - If projected stock falls below that, request enough to get back to the reorder point plus 30 days of cover. Take one V-belt. It shipped 240 units in 60 days, so 4 a day. The supplier needs 14 days, so the reorder point is 4 × 21 = 84. The Bin says projected quantity is 70. The nightly job raises a Material Request for 84 − 70 + 120 = 134 units. Leena looks at it over coffee and turns it into a Purchase Order. Or she doesn't, because she knows a big customer just went bust. The job proposes. A human buys. The code on this page is the core of that job. Around it sit a Reorder Rule DocType where Leena sets lead time and safety days, and a report that shows why each request was raised. ### Requests we'd argue against **Negative stock "just for now".** Both platforms let you switch it on. Valuation gets messy fast, and untangling it later costs someone a week. We'd rather fix whatever makes people want it. **Serial numbers on every screw.** Serials make sense for items with warranties or service history. For consumables, a batch is plenty. Often nothing is. **A quick "fix quantity" button.** Corrections belong in Stock Reconciliation (ERPNext) or an inventory adjustment (Odoo), with a reason. Anything that edits quantities outside the ledger will eventually meet your accountant, and it won't go well. **Syncing five marketplaces in week one.** Get the internal numbers right first. ### Leaving the spreadsheet behind Most people arrive with an Excel file, or three. We generate an import that loads items, warehouses and counted quantities as a single dated posting on your go-live day, so opening value is booked once. Do a physical count the weekend before. Yes, really. A spreadsheet you don't trust becomes a system you don't trust, just with nicer menus. ### Where inventory meets the rest of the ERP Stock matters because something moves it. Receipts come from [purchase management](https://erpfly.com/modules/purchase-management/), deliveries follow [sales orders](https://erpfly.com/modules/sales-order-management/), and if you need bins, putaway and pick lists inside each building, that's [warehouse management](https://erpfly.com/modules/warehouse-management/). Distributors should read how we approach [ERP for distribution businesses](https://erpfly.com/industries/distribution/). Still choosing a platform? The [ERPNext vs Odoo comparison](https://erpfly.com/compare/erpnext-vs-odoo/) covers how each one handles stock. ### FAQ ### ERPNext and Odoo already manage inventory. Why would I generate anything? If the standard reorder levels, batches and stock counts fit, you shouldn't. People come to us when their rule is different, like usage-based minimums, approval on adjustments, or expiry rules by product family. We generate only that difference and leave the rest of the stock module alone. ### Will a custom inventory module break when I upgrade? It lives in its own Frappe app or Odoo addon and doesn't touch core files. Stock is a busy area in both platforms, so run the included tests after a major version jump and read the release notes for stock changes. Budget an hour for it. ### Can we move our stock from Excel, Tally or QuickBooks? Yes. We generate an import for items, warehouses and opening quantities, posted as one dated Stock Reconciliation in ERPNext or an inventory adjustment in Odoo. Count the stock physically first, though. Importing numbers you don't trust just gives them a nicer font. ### Do barcode scanners work with this? Any scanner that types like a keyboard works in both ERPNext and Odoo forms. Odoo's dedicated Barcode app for handhelds is Enterprise only. If you need scan-heavy picking by bin, look at the warehouse management module instead. ### Who owns the code, and can our own developer change it? You own it. It's a normal app or addon in your Git repository with a README, so any Frappe or Odoo developer can pick it up. Nothing stops working if you leave erpfly. ### How long does it take? A first version of a reorder module usually appears within minutes. Expect a week or two of letting it propose requests alongside your buyer before you trust it, and that week is well spent.