Designing Point-of-Sale Systems

April 30, 2018

While point-of-sale (POS) systems belong to a unique software niche, they also display a surprising degree of variety. Like most old software, POS systems may have originated in the garages of small software innovators or established industry manufacturers. However, recently, POS systems have started transitioning into the realm of Web-based applications and mobile apps. This trend poses challenges to user-interface designers, who must be aware of how the design of POS systems differs from the design of other Web and mobile apps.

The Evolving World of POS Design

In bricks-and-mortar stores, cashiers use point-of-sale systems software, which functions as a digital cash register. Historically, POS systems have resembled embedded software systems because they rely on custom hardware. Plus, the contexts in which POS systems are used are professional settings, and they may receive heavy use by trained operators. However, the reality is more nuanced: many POS operators get little training because the turnover of staff is so high that they don’t have time to develop the mastery that is necessary to operate traditional embedded systems. Today, most new POS systems work either on a mobile phone or a tablet with a touchscreen, so gestural design patterns are making their way into the world of POS user interfaces.

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The Context of Use for POS Systems

Cashiers use POS systems in high-pressure, real-life settings. The challenge for operators is that they must very quickly check out customers’ purchases or queues will form and customers will become dissatisfied. Efficiency is more than an aspiration. Most cashiers that we have interviewed describe how genuine anxiety builds up with every new customer waiting in line. After all, the POS app is just a tool they use in human-to-human interactions.

But being quick is not the only requirement. Cashiers must be exact in their operation of the system because all of the data the system generates gets fed into complex accounting routines. Mistakes are not permissible and accounting rules are inflexible. Consequently, correcting a minor mistake may require a big effort and come back to haunt cashiers with little time on their hands.

Design Goals for the POS Context

While speed and accuracy are two objectives that every cashier tries to work toward, the contexts in which POS systems are used can differ significantly—from a small store with little traffic to a gas station that experiences sudden onslaughts of dozens of customers to a large store such as a supermarket, in which checkout points experience a constant flux of customers and cashiers must handle a stream of products that comes to them on a conveyor belt. These varied contexts generate very different specifics around the common tasks cashiers must perform, as well as common mistakes and necessary policies.

Many cashiers must both scan the products and operate the POS system’s user interface. Designers must consider what shortcuts the POS app’s user interface can provide, the user journeys, and the amount of information to display at each step. User interface designers should be mindful of all these factors, including the physical setup at the locations where cashiers will use the system.

One of the most important factors affecting the design of POS systems is the set of policies that are in place within the organization the POS system serves. These policies relate to issues such as whether and how a cashier can reverse a transaction—that is, cancel an item—how to apply discounts, and what currencies to accept. Ultimately, all of these elements impose limitations on a design because, most of the time, they are less than ideal from a UX perspective. They are usually devised for the benefit of the business, not the good of the user.

Clearly, the design parameters for a POS system differ greatly from those of a typical consumer app. Therefore, a few less common design principles are useful in guiding the efforts of designers to deliver great products that reconcile user needs with business needs.

Evolving Proficiency

Cashiers may receive some training on how to operate a cash register, but, most of the time, other more experienced cashiers help them to learn on the job. Designers may be tempted to make design decisions that favor first-time users, which is not a bad idea as long as this is a conscious decision.

However, it is worth keeping in mind that, after weeks of working with the software, users will sooner or later become proficient. Categorize the use cases based on their frequency and importance to the business.

The Difficulty of Updating the User Interface

While taking a minimum viable product (MVP) approach might be great for the design of most online applications, this may be counterproductive with POS systems. Cashiers need a great tool from the very first time they have to use it, so the burden must be on the software provider, not the user.

Furthermore, because cashiers use the POS interface daily for many hours, it is inevitable that strong routines develop. Thus, every future change to the user interface will involve unlearning their existing routines and learning new ones. Until the full adoption process has taken place successfully, these changes will generate a lot of mistakes and user frustration. Users learn such routines unconsciously, through repetition, so performing a mental override every time is exhausting to them.

Designing for the Context

Designers must be very clear about who they’re designing for and study the work patterns of the cashiers who operate the software. Be mindful of the following things:

the layout of the store and the cash desk
the shift system and how it relates to the ebb and flow of customers
the types of products customers buy

Most likely, you must design a POS system to be used for hours on end. Operators will become accustomed to the system, which can be both positive and negative.

The Challenges of Customization

Sometimes, the best way to solve a thorny issue in UX design is to let the user customize the user interface. However, while this may sometimes hold true for POS systems, the reality is that it can be challenging to make customization work.

For example, you may have multiple cashiers using the same open session on a POS system. Plus, to avoid fraud and mistakes, businesses may want to limit and control what operators can do. Cashiers may be inclined to process certain requests in ways they think is okay, even though they are not the preferred ways. In reality, businesses shun such practices because they create accounting problems. The job of the designer includes helping the business to reduce the frequency of unwanted behaviors.

The Necessity of Testing

Whatever designers dream up in the lab, it will never be sufficient for real-life POS users. The reality of POS-system usage can be too complex for designers to handle it well in the abstract. Therefore, testing is critical. Unfortunately, testing is difficult in such an ecological environment because it is not possible to make customers wait. Plus, a POS system’s database connections mean you must have a fairly refined product in place for testing. It is necessary to deploy novel testing paradigms to ensure the software fits the context of use.

Conclusion

In this article, I’ve given you an overview of the factors that affect the design of POS user interfaces. I’ve highlighted how these POS apps differ from other Web and mobile apps and how designers can design better POS systems by being mindful of some basic principles. In my article “The 16 UX Factors in the Point of Sale System,” I’ve provided more detailed design guidance that is based on numerous assignments designing POS systems and user research that I’ve carried out in several countries.

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