Batch Management and First-In-First-Out (FIFO) —— Consistency Between Records and Inventory, Preventing Stock Deterioration

Summary: Despite having three months of accumulated materials in the warehouse, production took the batch number from yesterday's delivery, and the month-end inventory discrepancy could not be resolved—this is a typical symptom of FIFO (First-In-First-Out) being out of control. This article delves into the underlying logic of batch management, clarifies the relationship between physical FIFO, system FIFO, and traceability, and provides practical solutions tailored to different industries and scales.

1. Case Study: A Label Triggers a Series of Inventory Discrepancies

A monthly inventory check at an electronics assembly plant revealed that the recorded balance of Class A materials was 8,500 pcs, but only 6,230 pcs were found on-site, resulting in a discrepancy rate of 26.7%. The investigation uncovered the following issues:

• Material Withdrawal Process: The warehouse staff, to save effort, took materials from the outermost (most recently arrived) boxes, leaving the batch from three months ago at the bottom.
• Shelf Life Expiry: The batch of electrolytic capacitors at the bottom had expired 47 days ago, but the system still showed them as "good for issue."
• Traceability Breakdown: A customer complained about an unusually high failure rate in a batch of power modules, but it was impossible to confirm whether the expired capacitors were used.

The root cause was clear: FIFO was not properly implemented, rendering batch traceability meaningless. This is not an isolated incident—APICS surveys show that approximately 62% of manufacturing companies have issues with FIFO implementation in their warehouses.

2. Three Core Elements of Batch Management

2.1 What is a Batch?

A batch (Batch / Lot) is a "homogeneous unit produced under the same conditions." From a quality perspective, the basis for batch division includes:

Key principle: The finer the batch granularity, the higher the traceability accuracy, but the higher the management cost. Companies should set a tiered batch strategy based on the product risk level—high-risk materials by furnace/tank/vessel, general materials by day/shift.

2.2 The Underlying Logic of FIFO

FIFO is not just an "first in, first out" operational rule; it addresses three core issues:

1. Shelf Life Control—ensuring materials are consumed within their shelf life, reducing expired scrap.
2. Traceability—the stricter the batch constraints, the smaller the scope of containment needed when anomalies occur.
3. Inventory Health—preventing the hidden accumulation of stagnant materials, avoiding situations where "materials are on the books but not in the warehouse."

There are three typical failure modes of FIFO:

Additionally, there is a less obvious hidden failure mode—lack of FIFO in reverse logistics. When nonconforming materials are returned or reworked materials are re-entered into inventory without reassigning batches or managing FIFO, these "return materials" often become the source of chaos. Companies should clearly state in their reverse logistics SOP that reworked or returned materials must be reinspected and assigned a new batch number before entering the normal FIFO cycle.

2.3 The Relationship Between Batches and Traceability

A batch is the smallest unit of traceability. A complete traceability chain consists of three links:

Raw Material Batch Number → Production Batch Number → Finished Product Serial Number/Batch Number
    ↓           ↓           ↓
Supplier Traceability   Process Traceability   Customer Traceability

The outbound sequence of FIFO directly affects the correspondence between raw material batch numbers and production batch numbers—if a raw material batch number is skipped during outbound, the "destination" of that batch becomes unclear. The precision of FIFO execution directly determines the upper limit of traceability system reliability.

2.4 Batch Number Coding Standards

Batch number coding is the infrastructure of batch management. A good batch number coding system should meet the following principles:

• Uniqueness—no repetition across the entire company to avoid confusion across different sites or years.
• Parsability—key information such as production date, production line, and shift can be directly read from the batch number.
• Machine Readable—carried by barcodes or QR codes, supporting quick identification by barcode scanners and PDAs.

Recommended format example: YYYYMMDD-LL-BB-NNN, where YYYYMMDD is the production date, LL is the production line code, BB is the shift code, and NNN is the daily serial number. For instance, 20260716-P2-B-028 indicates batch 28 from shift B on production line P2 on July 16, 2026.

In practice, many companies use overly complex batch number coding (embedding too much redundant information) or overly simple coding (only serial numbers), the former leading to reluctance among frontline staff to manually record, and the latter necessitating the manual review of logs for traceability. It is recommended to find a balance between simplicity and information content—barcodes carry all information, while the human-readable part only includes core search fields.

3. Four Typical Implementation Schemes for FIFO

There is no one-size-fits-all "best FIFO scheme"; different warehouse configurations, levels of automation, and industry requirements dictate different choices.

Scheme A: Physical FIFO Storage Design (Low Investment)

Suitable for manual warehouses and small to medium-sized enterprises, without the need for WMS system support.

• Gravity Racks: rear loading, front unloading, naturally forming FIFO.
• FIFO Lanes: sub-storage positions are created for the same SKU, arranged in batch sequence, and the next lane is opened only after the current one is fully depleted.
• Batch Color Coding: different colored labels are used for each month's arrivals (January = Red, February = Blue, etc.), and warehouse staff take materials according to color.
• Layer Rules: new batches are placed on the upper layer/rear, and withdrawal starts from the lower layer/front.

Advantages: zero system cost, visual management can be implemented on-site. Disadvantages: depends on personnel discipline, prone to deformation when shifts or personnel change.

Scheme B: WMS System FIFO Recommendation + Manual Confirmation

Suitable for medium-sized enterprises that have implemented WMS.

• The system recommends outbound storage positions based on batch number sequence.
• Warehouse staff confirm by scanning, and the system alerts if the wrong batch is taken.
• A "mandatory FIFO" control switch is set—materials with shelf life requirements cannot skip batches during outbound.

Key detail: the FIFO sorting logic in the system must be based on receiving time + batch number dual-field sorting; sorting by batch number alone can lead to "cross-day batch" issues.

Scheme C: Automated High-Bay Warehouse FIFO

Suitable for high-flow, high-value raw materials in automated warehousing scenarios.

• Stackers automatically retrieve designated pallets according to system instructions.
• Batch information is synchronized to MES, and raw material batch numbers are automatically verified against the work order FIFO requirements during feeding.
• Abnormal batch numbers are automatically locked, preventing feeding.

Scheme D: Lean FIFO Channel (Pull Production)

Suitable for line-side warehouses and continuous flow production lines, typical methods from lean manufacturing:

• Set up FIFO channels between two processes (marked and defined capacity, one-to-one correspondence).
• If the channel is full, the upstream line stops; if the channel is empty, the downstream line stops.
• Each position corresponds to a specific batch.

This scheme addresses both inventory upper limit control and batch sequence issues, serving as a foundational element in lean production line design.

4. Self-Inspection Checklist for Batch Traceability Capability

Use the following checklist to assess the current batch management level of your factory:

Each non-compliance item should be included in the improvement plan. Batch management is not an "one-time implementation" IT project but a foundational capability that requires daily maintenance and periodic review.

4.1 On-Site Random Sampling Method for FIFO Compliance

Many companies have established FIFO policies but have never quantitatively assessed their implementation. The following method can be completed within half an hour:

1. Random Sampling—select 10 storage positions at random in the warehouse and record the receipt dates of the oldest and newest batches in each position.
2. Calculate FIFO Deviation—check the last 20 outbound records in the system and compare the actual outbound batches with the system-recommended FIFO batches.
3. Trace Abnormal Batches—pick 1-2 batches that have exceeded their shelf life and trace whether they still exist in inventory.

Incorporate the sampling results into the monthly performance evaluation of warehouse personnel to quickly establish discipline in FIFO execution. If the FIFO compliance rate is below 95% for three consecutive months, it indicates a design flaw in the system and process, not an issue with employee compliance.

5. Common Misconceptions

Misconception One: FIFO = "Outbound Sequence"

Correction: FIFO is not just an outbound sequence but a mechanism for managing inventory health. Even if the warehouse is fully WMS-automated, if regular inventory checks and handling of abnormal batches are not performed, the FIFO in the system is just an illusion.

Misconception Two: The Finer the Batch Granularity, the Better

Correction: Overly dividing batches significantly increases the workload for inspection, labeling, and traceability. It is recommended to adopt a differentiated batch strategy based on product risk levels—high-risk materials with three-level traceability (raw material → process → finished product), and low-risk materials by daily batches.

Misconception Three: ERP FIFO Sorting is Reliable

Correction: ERP batch recommendations are based solely on system receipt times. If there are on-site violations such as "skipping batches and then modifying system records," the ERP FIFO recommendation loses its practical significance. The reliability of system FIFO depends on on-site execution discipline.

6. Phased Implementation Roadmap

Improvements in batch management and FIFO do not have to be implemented all at once. Based on the company's resources and urgency, it is recommended to proceed in three phases:

Phase One: Foundation Building (1-2 Months)

• Review all inventory materials and define batch control requirements based on risk levels—high-risk materials (pharmaceuticals, food-grade raw materials, electronic components) must be defined as independent batches by furnace/tank/box.
• Standardize batch number coding rules, update batch number fields in ERP/WMS, and clean up dirty records in historical inventory where batch numbers are missing.
• Train warehouse staff and production line material handlers on basic FIFO operational requirements—emphasize "why" rather than "what."
• Establish a standardized process for batch number labeling (label position, anti-fall measures, re-printing rules), and clearly define the specific responsible persons for each production line and storage area.
• Conduct the first round of FIFO compliance rate baseline measurement and record the current deviation rate as a benchmark for subsequent improvements.

Phase Two: System Integration (2-4 Months)

• Enable FIFO recommendation outbound function in WMS and set the mandatory FIFO rule switch.
• Add raw material batch number scanning verification in the MES feeding process.
• Implement automatic locking of expired materials to prevent outbound and feeding.
• Establish automatic statistical reports for FIFO compliance rates.

Phase Three: Lean Optimization (Ongoing)

• Analyze FIFO deviation data to identify system bottlenecks and operational blind spots, and develop targeted improvement measures.
• Optimize warehouse layout—move high-turnover and high-risk materials to storage areas suitable for FIFO, reducing the frequency of manual searching.
• Introduce a mock recall drill mechanism, conducting full-chain traceability tests every six months—randomly select a batch number from finished products and complete the entire traceability loop from raw materials to customers within 48 hours.
• Incorporate batch management levels into the supplier audit system, requiring key suppliers to provide batch-level traceability capability proof.
• Establish a batch management KPI dashboard, including indicators such as FIFO compliance rate, expired material ratio, and traceability completion time in daily operational monitoring.

The essence of batch management is not the IT system, but on-site discipline.

Knowledge Number: 9.3.1

Version: v20260716

Author: Quality Excellence Think Tank Quality Excellence Think Tank is dedicated to providing systematic professional knowledge, methodologies, and practical tools to quality management practitioners, helping companies continuously improve their quality capabilities.