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How Many Order Picking Errors Go Unreported?

How can you detect unreported errors? And how can you correct the flaws?

General Inquiry

voice directed order picking

Most operations maintain at least some numbers on the most critical aspects of the business. For order picking operations, you might track number of orders picked per day, hours per pick, cost-per-pick, on-time rates — and error rates. The question is this: how accurate are those numbers? For instance, if your system reports 50 order picking errors a week, does that represent half your errors? All of them? Most of them? It’s can be difficult to understand.

One warehouse manager told us that he believed that something in the range of “44 to 60%” of errors go undetected in his operation.

Quantity based (too many, or too few) errors demand different solutions than errors caused by mis-picks. Filling cartons is an entirely different situation than filling pallets or dealing with something that is assembled in the process and shipped as a single unit.

Cycle counts are your friend

The counts won’t add up if there are consistent errors. Finding information that compares returns to cycle counts to reported errors can help you understand the situation. While this method won’t always give you a definitive answer, it will help you find some percentage of the unreported errors. It’s a mile-high look at the situation. If it’s consistently off, there is an issue. It might be order picking, it might be receiving, might be a pilferage problem. But you’ll know that one way or another, something isn’t in alignment and that you can pursue the issue more thoroughly.

Traceability is critical in this process. While automated systems like pick to light and carousels can help reduce these problems, they are not a cure-all. People are still capable of making mistakes, so the ability to trace the problem from receiving through putaway and picker to packer is highly important.

Over-picks are under-reported, but how can you detect them?

When you ship the wrong item, or not enough things, or miss one on a multi-line order, customers almost always communicate this back to you. But  when you over pick and ship more than the amount ordered, some customers may not report that error.

A few years ago, I purchased a Mac Book Pro, and was shipped two. My shipping documents said that I’d received only one; I could have kept the extra computer. When a relatively large, highly expensive laptop can be double-picked, how many smaller items are? And what’s the cumulative cost? That picking error may never be detected.

Identifying over-picks is difficult, and the best chance you have to eliminate them is a system of quality and double checks at both the picking and packing level.

Manual checking and double checking

All order picking operations commit mis-pulls.

Training your pickers, and having methodology to check the quality of work is one of the least expensive ways to detect and reduce errors. This may involve packers checking the pickers’ work. It may involve dedicated quality assurance associates. If pickers pack cartons on the line, consider using cross-checks with other pickers so that there is another set of eyes on the order. That may slow the operation down, but if it detects enough mistakes that you can identify and address the issue, it’s all worthwhile.

Compare reported errors to inventory adjustments

Start with your reported errors and match them against inventory adjustments. Unexplained adjustments that don’t match with the errors are an excellent place to begin your search for error types. Obviously, we tend to come back to over-picks or even mis-picks where customers received a higher-value item than the one they ordered and paid for.

Some tips on reducing unreported errors

  • Employ quality control associates. Yes, this is expensive, but it can dramatically reduce the cost of errors, returns, dissatisfied customers, and associated costs.
  • Revise and improve inventory slot marking. This is not an expensive proposition, but it does take time and consistent effort. Make sure it’s easy to identify product slots. Don’t stock similar looking items directly next to each other. Be sure your pickers understand where the slots are located and that a relatively new employee can pick it up without significant training and experience.
  • Understand the cost of mis-picks. You won’t know whether the effort to reduce these errors is worthwhile until you understand how many there are, and what it costs you.
  • Pay attention to security issues. It goes without saying that high-value inventory — and plenty of lower value items as well — have a tendency to walk away. Employees bent on stealing inventory can get very creative in the ways they mask theft and this is essentially an unreported error.
  • Utilize incentives, but be specific and demanding. While most people are honest, many won’t hesitate to game numbers when there is a potential gain for them. Many factors will affect the approach.  Make sure any incentives encourage the desired outcome.
  • Be sure to understand how various hands-free systems might help you.  See our guide that compares voice, pick to light, and RF alternatives.

Also, see our guide to reducing inventory errors. As you work to understand your unreported error rate, you’ll find issues that can also help you in other areas of your operation.

Scott Stone is Cisco-Eagle's Vice President of Marketing with more than thirty years of experience in material handling, warehousing and industrial operations. His work is published in multiple industry journals an websites on a variety of warehousing topics. He writes about automation, warehousing, safety, manufacturing and other areas of concern for industrial operations and those who operate them.

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