What Is Amazon's IPI Score?
Amazon's Inventory Performance Index (IPI) score is a critical metric that measures how efficiently you manage your FBA inventory. It ranges from 0 to 1000, with anything above 350 considered acceptable and above 500 considered excellent. Your IPI score directly affects your selling privileges and storage fees, making it one of the most important numbers in your FBA business.
The Four Factors That Determine Your IPI Score
Amazon calculates IPI using four primary metrics:
- Excess Inventory: The percentage of inventory that hasn't sold in 90 days. Higher excess inventory lowers your score. Target: Less than 10% excess.
- Sell-Through Rate: The percentage of inventory that sells within 90 days. Higher sell-through improves your score. Target: Above 90%.
- FBA Fulfillment Rate: The percentage of orders fulfilled by FBA vs merchants. Higher FBA rate improves your score. Target: Above 95%.
- Stranded Inventory: Items without current buy boxes or listings. These dramatically hurt your score. Target: Zero stranded inventory.
Why IPI Score Matters: The Real Consequences
If your IPI score drops below 350, Amazon will restrict your inventory limits. For sellers in growth phase, this is devastating. Additionally:
- Low IPI triggers higher long-term storage fees (45p per unit per month vs standard 15p)
- You may be temporarily suspended from FBA privileges
- Your account is flagged for compliance reviews
- Rebuilding a damaged IPI score takes 3-6 months minimum
How a Prep Centre Protects Your IPI: Factor 1 - Faster Inventory Turnover
The largest IPI impact comes from inventory turnover speed. Items sitting in transit from your facility to Amazon FC extend your "in-flight" inventory window, reducing sell-through rate calculations. When a prep centre handles logistics professionally:
- Faster Processing: Professional prep centres process shipments within 5-7 days. DIY prep can stretch to 2-3 weeks.
- Reliable Shipping: Prep centres use optimised logistics with predictable delivery. DIY means variable delivery times depending on your carrier choice.
- Consolidated Shipments: Smaller, frequent shipments mean inventory reaches Amazon faster on average. One 1,000-unit shipment might take 3 weeks; four 250-unit shipments handled by a prep centre reach Amazon in staggered periods, improving your average sell-through timeline.
How a Prep Centre Protects Your IPI: Factor 2 - Fewer Returns and Rejections
When Amazon rejects your shipment due to labelling errors, incorrect quantities, or damaged goods, those units don't reach the FC. They get sent back, creating a 3-6 week delay that tanks your sell-through rate. A prep centre eliminates this risk:
- 99.8% Acceptance Rate: Professional prep centres achieve first-time acceptance rates above 99%. DIY prep often sees 5-10% rejection rates due to labelling errors or quantity mismatches.
- Quality Control: Every unit inspected before shipment. Damaged goods are set aside before they enter Amazon's system.
- Compliance Certainty: Proper FNSKU placement, polybagging, and documentation mean zero compliance rejections.
How a Prep Centre Protects Your IPI: Factor 3 - Accurate Inventory Management
Stranded inventory (listings without buy boxes or active offers) is an IPI killer. This happens when:
- You deactivated a listing but inventory is still in the FC
- Quantity mismatches between your records and Amazon's
- Pricing errors that make the item uncompetitive
A prep centre's detailed shipment tracking and documentation help you maintain accurate inventory records. You always know exactly what's in the FC and when it arrived, making it easy to spot and resolve stranded inventory quickly.
How a Prep Centre Protects Your IPI: Factor 4 - Better Inventory Distribution
For larger sellers shipping across multiple Amazon FCs, a prep centre can strategically distribute inventory to balance sell-through rates across locations. This optimises your IPI across all FCs rather than concentrating inventory in slow-moving locations.
Real-World IPI Impact: A Case Study
Consider a seller with 3,000 units across 5 SKUs:
- DIY Prep Scenario: Prep and ship takes 4 weeks. Items sit in transit 5-7 days. Sell-through calculation window extends 25-30 days, reducing sell-through rate by 8-12%. Two shipments rejected due to labelling errors, adding 3 weeks delays. IPI score drops from 600 to 420 (critical level).
- Prep Centre Scenario: Prep and ship takes 7 days. Items in transit 5 days. Sell-through calculation window 12 days. 99.8% first-time acceptance means zero rejections. IPI score improves from 600 to 750 due to faster turnover and zero rejections.
The difference: One seller's growth is restricted; the other scales freely.
Additional Benefits Beyond IPI Protection
Using a prep centre protects your IPI while offering broader advantages:
- Time for Growth: Instead of managing prep, you spend time optimising listings, running PPC campaigns, and finding new products.
- Risk Reduction: Your account isn't at risk of compliance violations or low scores due to handling errors.
- Scalability: You can expand to 5,000, 10,000, or 50,000 units without operational strain.
IPI Maintenance Checklist
- Use a prep centre to ensure fast, reliable shipments to Amazon FC
- Monitor sell-through rates monthly; target above 90%
- Identify and clear stranded inventory within 48 hours of discovery
- Maintain excess inventory below 10% through accurate demand forecasting
- Keep FBA fulfillment rate above 95%
- Request detailed shipment reports from your prep centre to verify receipt at Amazon FC
The Bottom Line
Your IPI score is the health indicator of your FBA business. A prep centre protects this score by ensuring fast, accurate shipments with zero rejections. For serious FBA sellers, this protection alone justifies the outsourcing cost. PrepExpress's 99.8% first-time acceptance rate and fast processing have helped hundreds of UK sellers maintain and improve their IPI scores while scaling their businesses. If your IPI is currently below 500 or you're concerned about it dropping, it's time to consider outsourcing to a professional prep centre. Let's protect your growth together—contact PrepExpress for a consultation.