Inventory accuracy is the percentage match between what the WMS says is on hand and what’s actually on the shelf. It’s measured by counting a sample of bin locations, comparing counts to the WMS, and dividing the matched locations by the total counted. A typical Vertex SLA targets 99.0% or higher on cycle counts at the location level. Below 95% accuracy, oversells, stockouts, and customer service tickets compound quickly.
How it works in practice
Cycle counting is the operational discipline that maintains inventory accuracy. Instead of shutting down the warehouse for a full annual physical, a small percentage of locations are counted every day. The cycle is structured by ABC velocity (A-items counted monthly, B-items quarterly, C-items semi-annually), or by location type (forward pick counted more frequently than reserve). Variances are investigated immediately. The WMS adjustment ties to a reason code: pick error, putaway error, damage, theft, or system glitch.
Best-in-class operations don’t just hit a number, they trend the reason codes. If 60% of variances are putaway errors, the fix is in the receiving process. If 60% are pick errors, the fix is at pack-out.
Why it matters
Inventory accuracy below 99% means oversells, which means cancelled orders, refunds, and customer trust loss. It also means a brand can’t trust its replenishment forecasts, since the WMS numbers don’t match reality. Brands that operate at 99.5%+ inventory accuracy can run leaner safety stock and reorder closer to actual demand. Brands at 95% are perpetually firefighting.
Common misconceptions
- Inventory accuracy is not the same as unit accuracy. A location can be 100% match by count but contain the wrong SKU. Most modern measurements use location-level match.
- 100% inventory accuracy is unrealistic at scale. The cost of the controls needed to hit it exceeds the benefit. 99.0%-99.5% is the practical target for most ecommerce 3PLs.
- Inventory accuracy is a process metric, not an event. A clean physical inventory once a year is meaningless if cycle counting is undisciplined the other 364 days.