Your Shopee PH store just sold the last unit. Your Lazada PH store still shows 3 available.
You are now oversold.
That gap — between what your records say and what is on your shelf — is what inventory systems exist to close. The choice between a perpetual inventory system and a periodic inventory system determines how wide that gap gets.
This guide explains both systems, how they work for Philippine ecommerce sellers, and which one fits your operation.
What Is a Perpetual Inventory System and How Does It Work?
Your stock count updates the moment a sale, return, or purchase happens.
A perpetual inventory system is a real-time stock tracking method where inventory records are updated continuously after every transaction. Based on seller community feedback and operations practice across Philippine ecommerce, perpetual systems become the practical standard for businesses processing more than 200 transactions per month, as manual periodic counts cannot keep pace with transaction volume at that scale.
With a perpetual system, every sale on Shopee PH reduces your recorded stock count immediately. Every incoming shipment from your supplier adds to it. Every return adjusts it. At any moment, your system’s count should match — or come very close to matching — what is actually in your warehouse.
Tools like Ginee and Sellercraft both operate on the perpetual model — they pull order data from Shopee PH and Lazada PH via API and adjust stock counts in near real-time. Each transaction records the SKU, quantity, transaction type, timestamp, and remaining stock after the adjustment.
The result: you can query your stock level at any moment and get an accurate answer without counting anything.
The major limitation: perpetual systems are only as accurate as the data going in. If a marketplace sale fails to sync, if a supplier shortships without your team catching it, or if products are damaged and not recorded, the system drifts from reality. Most sellers do a physical count once per quarter to reconcile.
What Is a Periodic Inventory System and How Does It Work?
You count everything at fixed intervals — daily, weekly, monthly, or quarterly.
A periodic inventory system is a stock tracking method where inventory is physically counted at set intervals, and records are updated in bulk after each count rather than after each individual transaction. Between counts, the system does not reflect sales or adjustments — the current stock level is unknown until the next count occurs.
In a periodic system, the sequence works like this: You start a period with a known opening stock count. During the period, all purchases are recorded (so you know what came in). At the end of the period, you count everything physically. Cost of Goods Sold (COGS) is calculated after the fact: opening stock + purchases received − ending stock count = goods sold during the period.
This is the method most Philippine sellers start with — especially those running small single-channel operations on a spreadsheet. It requires no special software and works well when transaction volume stays low.
Typical periodic counting schedules:
- Daily counts: for fast-moving items at high stockout risk (e.g., promotional products during Shopee 11.11)
- Weekly counts: standard for sellers with 50–300 monthly orders
- Monthly counts: common for slower-moving inventory and seasonal products
- Annual counts: for businesses treating inventory primarily as a financial exercise
What Is the Key Difference Between Perpetual and Periodic Inventory Systems?
The difference is timing — when your stock records reflect reality.
The key difference between perpetual and periodic inventory systems is update frequency: perpetual systems update stock counts in real time after every transaction, while periodic systems update counts only after a scheduled physical stock count. This difference determines how much time elapses between a transaction and its reflection in your records.
| Factor | Perpetual Inventory System | Periodic Inventory System |
|---|---|---|
| Update frequency | Real-time, after each transaction | After each scheduled count |
| Stock accuracy between counts | High (reflects recent transactions) | Unknown (count is the only anchor) |
| Technology required | Inventory software or WMS | Spreadsheet is sufficient |
| Setup cost | PHP 1,500–8,000/month for software | Low to zero (spreadsheet-based) |
| Overselling risk | Low (stock deducted at time of sale) | Medium to high (no real-time deduction) |
| Physical count required | Yes, but less frequently (quarterly is common) | Yes, at every count interval |
| COGS calculation | Continuous, computed per transaction | Period-end, calculated retrospectively |
| Best for | Multi-channel sellers with 200+ monthly orders | Single-channel sellers under 100 monthly orders |
Thresholds above reflect common practice per seller community feedback; specific numbers vary by product type, SKU count, and warehouse complexity.
Which System Do Philippine Ecommerce Sellers Actually Use?
Most start periodic, most grow into perpetual — the switch point is earlier than sellers expect.
Based on seller community discussions on Shopee PH seller forums and Facebook groups, the majority of Philippine ecommerce sellers start with periodic inventory (spreadsheet-based) and transition to perpetual tracking when managing 2+ marketplaces or when overselling incidents begin causing order cancellation penalties from Shopee or Lazada PH.
Single-channel sellers on Shopee PH with under 100 orders per month typically manage with a weekly count on a spreadsheet. The math is straightforward, the tools are free, and the volume does not justify software costs.
The inflection point comes at one of three triggers:
Opening a second marketplace. Once you are selling on both Shopee PH and Lazada PH from shared stock, periodic tracking means one channel does not know what the other sold. Overselling becomes structurally likely.
Hitting 200+ monthly orders. At this volume, daily counts become a significant time drain away from sourcing and customer service.
Receiving a cancellation penalty. Shopee PH issues seller penalties for unfulfilled orders. A single overselling incident can cost more than a month of inventory software.
Periodic inventory is a starting point, not a long-term system for growing Philippine ecommerce operations.
Does your current inventory setup leave you operating blind between counts? Use the InventoryFlow Scorecard to check where your inventory system stands — takes under 5 minutes, no signup required.
When Should You Switch from Periodic to Perpetual Inventory?
Switch when the cost of not knowing exceeds the cost of the software.
Philippine ecommerce sellers should switch from periodic to perpetual inventory tracking when they meet any of these conditions: selling on 2+ marketplaces from shared stock, processing more than 200 orders per month, managing more than 100 active SKUs, or having experienced an overselling incident that resulted in marketplace penalties or buyer complaints.
Entry-level inventory software with Shopee PH and Lazada PH integration starts at roughly PHP 1,500–2,500 per month (based on published pricing as of mid-2026). A single Shopee PH cancellation penalty or lost repeat customer from an out-of-stock can easily exceed that monthly cost.
Switching checklist for Philippine sellers:
- You sell on Shopee PH and at least one other channel (Lazada PH, TikTok Shop PH, your own website)
- You process 200+ orders per month across all channels
- You carry 100+ active SKUs
- You have experienced an overselling incident in the last 90 days
- Your weekly or daily stock counts take more than 2 hours each
If three or more of these apply, periodic inventory is costing you more than the software would.
How Do Perpetual Inventory Systems Handle Multi-Channel Shopee and Lazada Sync?
Stock deductions flow from each marketplace into a shared ledger in real time.
Perpetual inventory systems integrate with Shopee PH and Lazada PH via official marketplace APIs, pulling confirmed order data and deducting sold quantities from a shared stock pool within minutes of each sale. When configured correctly, a single inventory count in the system serves both channels simultaneously, eliminating the manual reconciliation that periodic tracking requires.
Here is how the sync chain works in practice:
Step 1: You set your total available stock in the inventory system (e.g., 50 units of SKU-A). The system pushes that quantity to both Shopee PH and Lazada PH listings simultaneously.
Step 2: A buyer purchases 2 units on Shopee PH. The marketplace confirms the order to the inventory system via API, which deducts 2 units from the shared pool — now 48 available — and immediately updates the Lazada PH listing.
Step 3: When you receive a restock of 20 units from your supplier and record the purchase receipt, the system updates both listings to 68.
Most Philippine sellers using Ginee or Sellercraft check their sync status daily — especially before promotions — because marketplace API rate limits can cause temporary delays. J&T PH and LBC courier integrations also feed fulfillment data back into the inventory system, marking items as shipped and preventing double-fulfillment.
What Are the Costs of Each Inventory System for Philippine Sellers?
Periodic costs almost nothing upfront; perpetual costs PHP 1,500–8,000 per month depending on volume.
For Philippine ecommerce sellers, periodic inventory has near-zero direct software cost (spreadsheet-based), while perpetual inventory software ranges from PHP 1,500 to PHP 8,000 per month for mid-tier tools that include Shopee PH and Lazada PH integrations. The cost comparison changes significantly when factoring in the time cost of manual counting and the penalty cost of overselling incidents.
Cost breakdown by system:
| Cost Category | Periodic Inventory | Perpetual Inventory |
|---|---|---|
| Software | PHP 0 (spreadsheet) | PHP 1,500–8,000/month |
| Time for stock counts | 3–10 hours/week at scale | Near-zero (automated) |
| Overselling risk cost | High — Shopee cancellation penalties + buyer complaints | Low — stock deducted at time of order |
| Physical count frequency | Weekly or more | Quarterly reconciliation |
| Setup effort | Low — build or download a spreadsheet template | Medium — configure SKUs, connect marketplaces, test sync |
Pricing data above is based on published software pricing available to Philippine sellers as of mid-2026; individual plans and discounts vary. Read our complete inventory software guide for Philippine sellers for current pricing breakdowns and tool comparisons.
The true cost of periodic tracking is not the spreadsheet — it is the opportunity cost of the hours spent counting and the risk cost of the counts that are late or missed.
Frequently Asked Questions
What is the main difference between perpetual and periodic inventory systems?
A perpetual inventory system updates stock counts in real time after every sale, purchase, or return. A periodic system only updates records after a scheduled physical count. For Philippine ecommerce sellers running multiple marketplaces, perpetual tracking prevents overselling between counts — something periodic systems cannot do without daily manual recounts.
Can Philippine ecommerce sellers use a periodic inventory system with Shopee and Lazada?
Yes, but with significant risk. Periodic systems do not sync with marketplace order data automatically, so stock levels on both Shopee PH and Lazada PH will drift from reality between counts. This creates overselling risk that grows with order volume. Most sellers running both marketplaces from shared stock find periodic tracking unsustainable beyond 100–150 orders per month.
Which inventory method gives more accurate financial reporting?
Perpetual inventory provides more accurate, up-to-date COGS and financial reporting because transactions are recorded individually as they happen. Periodic systems calculate COGS retrospectively at period end, which means financial statements can only be prepared after a physical count. For Philippine sellers operating under BIR reporting requirements, perpetual records reduce the compliance burden at period close.
How long does it take to switch from periodic to perpetual inventory?
For a single-warehouse seller with under 500 SKUs, connecting inventory software to Shopee PH and Lazada PH and importing your current stock count typically takes 1–3 days. The first week involves reconciling sync discrepancies and confirming the API connection works. After that, the system runs without manual counts between quarterly reconciliation cycles.
Does a perpetual inventory system eliminate the need for physical stock counts?
No. Perpetual systems reduce the frequency of physical counts but do not eliminate them. System records drift over time due to unrecorded damages, supplier shortships, and data sync errors. Most Philippine sellers using perpetual inventory software do a full physical reconciliation count quarterly — comparing system records against actual warehouse stock and adjusting for any discrepancies found.