Whether you order weekly or quarterly, supplier performance impacts your margins, inventory accuracy, and customer experience. Many e-commerce teams overlook tracking KPIs for vendors — especially if they only order in large, infrequent batches.
That’s a mistake.
Even with quarterly orders, you should be tracking supplier data proactively — not just when things go wrong.
Here are the top 5 KPIs every e-commerce brand should track for suppliers, regardless of how often you place POs.
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1. On-Time Delivery Rate
What it measures:
The percentage of orders delivered by the promised delivery date.
Why it matters:
Late deliveries don’t just affect timelines — they ripple through your entire business: stockouts, ad pauses, missed launches, and warehouse bottlenecks.
Formula:
(On-time deliveries / Total deliveries) × 100
Modonix Tip:
Create a 90-day rolling average by supplier, even if you only order once per quarter. The first late shipment might be an excuse — the second is a trend.
2. Units Delivered / Units Ordered (Fill Rate)
What it measures:
The accuracy of what the supplier delivers vs. what you ordered.
Why it matters:
Partial shipments can throw off bundle availability, create SKU mismatches, and distort your true cost of goods sold (COGS).
Formula:
(Total units received / Total units ordered) × 100
Modonix Tip:
Use this KPI alongside inventory alerts — don’t find out you only received 95% of what you ordered after your FBA stock is depleted.
3. Invoice Accuracy Rate
What it measures:
The % of invoices that match the PO and delivery data — no price errors, double charges, or missing credits.
Why it matters:
Incorrect invoicing creates reconciliation friction, slows month-end reporting, and can lead to overpayment.
Formula:
(Accurate invoices / Total invoices) × 100
Modonix Tip:
Flag suppliers with less than 98% accuracy. Errors might seem small, but over time they erode your margin and drain your ops team.
4. Lead Time Variability
What it measures:
The difference between quoted lead time and actual delivery time — tracked over multiple orders.
Why it matters:
Inconsistent suppliers make it hard to plan ads, launch cycles, and promos — especially during seasonal demand spikes.
Formula:
Standard deviation of actual lead times
Modonix Tip:
Even if you order 4x/year, logging lead time drift helps you negotiate better terms or justify switching vendors when things go sideways.
5. Defect Rate or Return %
What it measures:
How often the products you receive are damaged, mislabeled, or don’t meet your spec.
Why it matters:
Defective inventory creates extra work at the warehouse, frustrates customers, and increases refund rates — especially if you resell on Amazon.
Formula:
(Defective units / Total units received) × 100
Modonix Tip:
Don’t wait for Amazon to suspend you — track defect rate early. If a vendor’s QC drops, address it before your listing gets flagged.
Bonus KPI for High-Frequency Buyers: Transit Time
What it measures:
The average number of days (or hours) it takes for goods to arrive from the time of dispatch to the time of receipt.
Why it matters:
For brands that place daily or rolling POs — especially those relying on just-in-time inventory, dropshipping, or daily fulfillment cycles — even a one-day delay can cascade into late shipments, ad throttling, or low stock alerts.
Formula:
(Date received – Date shipped)
Modonix Tip:
If you notice that transit time is increasing, it may signal upstream bottlenecks (like port congestion, carrier issues, or your supplier batching smaller orders inefficiently). Use this KPI to hold both suppliers and carriers accountable.
📊 Data That Backs This Up
Supply chain instability is no longer a rare event — it’s a baseline challenge for most e-commerce teams. At Modonix, we’ve seen how poor visibility into vendor performance leads to late shipments, bloated inventory, and hidden margin loss.
🧠 Pro Insight
Tracking Transit Time vs. On-Time Delivery gives you a dual lens:
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Transit Time tells you about shipping carrier reliability
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On-Time Delivery tells you about supplier lead-time accuracy
📚 Further Reading
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