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Lush: Custom Memo Cost Engine for ERPNext
How we built a bespoke Frappe app that gives Lush Cosmetics dual-cost visibility — budget-rate costing running in parallel with ERPNext's live FIFO valuation.
About the Project
Lush is a global handmade cosmetics manufacturer headquartered in Poole, Dorset. We previously helped Lush deploy ERPNext across 5 countries — covering production planning, finance, and inventory management.
This project focused on a specific challenge: building a custom Frappe app (lush_memo_cost) that adds a parallel "memo cost" (budget/planning cost) system alongside ERPNext's live FIFO valuation — giving finance teams the dual-cost visibility they needed for budgeting, pricing, and margin analysis.
Scope
19
Days
Cost
Fixed-Price
Engagement
Reports
6
Custom
Tech
Frappe v15
Custom App
The Challenge
FIFO ≠ Budget Cost
ERPNext's live FIFO valuation fluctuates with every purchase — unsuitable for budgeting, pricing, and margin analysis where stable, planned costs are essential.
Multi-Level BOM Complexity
Lush products have deep BOM hierarchies — finished goods, sub-assemblies, and raw materials. Budget costs must roll up accurately through every level.
Dual-Cost Reporting Gap
Finance needed to compare actual (FIFO) vs planned (memo) costs side-by-side across purchasing, stock, and sales — with no native ERPNext support for this.
The Solution
We built a standalone Frappe app that extends ERPNext with a complete memo cost system — from individual item costs through multi-level BOM roll-ups to dual-cost management reports.
Memo Cost Field
Custom field on Item and BOM DocTypes via Frappe's non-destructive Custom Fields — fully upgrade-safe with zero core changes.
Global Recalculation
Level-wise background engine that calculates memo costs from leaf BOMs upward, batched in 7,000-record chunks with Redis-cached dependency maps.
BOM Version Cascading
When a raw material BOM is upgraded, every parent BOM is automatically versioned and updated — cascading through the full hierarchy.
Currency Exchange Rate Memo
Dedicated DocType for storing budget FX rates, decoupled from ERPNext's live exchange rates — so budget costs remain stable regardless of currency fluctuations.
6 Management Reports
Purchase Order Analysis, Purchase Receipt Analysis, Stock Analysis, and Sales Margin Reports (Lvl 1-3) — all showing FIFO vs Memo costs side-by-side with variance columns.
Individual BOM Cost Update
Pressing "Update Cost" on any BOM recalculates both the standard ERPNext cost and the memo cost for that BOM version — keeping both cost systems in sync.
The Results
19 Days
Scoped and delivered
6 Reports
Dual-cost management reporting
Zero
Core changes required
Upgrade-Safe
Compatible with ERPNext updates
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