5 Ways to Win Back an Abandoned Shopping Cart We're talking the online kind, of course, and the lost revenues they pose for startups.

Companies lose $18 billion in sales every year from customers who abandon their online shopping carts. Between Black Friday and Cyber Monday alone, 79 percent of mobile phone shoppers ditched their carts, leaving a cringeworthy amount of money on the table. While shopping-cart abandonment strikes both large and small companies, it's a much bigger concern for startups.

Related: The Key to Converting Online Sales Leads: Speed

A quarter of online customers abandon their shopping carts because of complicated website navigation, and 21 percent ditch their transactions due to long checkout processes. Large retailers likely have the funds to address these problems. Startups, in contrast, often have limited resources, alongside their lower revenues. As more customers abandon their purchases, the lost sales create an unfortunate snowball effect: The rich get richer, and startups stagnate.

But fear not: Applying these five simple, low-cost strategies will increase conversions and lower your number of abandoned carts:

1. Poll before you build.

The best strategy for preventing shopping-cart abandonment appears early in the app-planning process. Before you build, research your customers to determine how they'd expect your app to work. Mock up the screens to put them in front of your customers before you build them. Knowing your customers and creating a user-friendly experience based on their expectations will undoubtedly increase sales.

Continue communicating with your customers throughout the building process. Have them test your app's features, and record their feedback. You'll learn what's most important to them -- whether that means speed, efficiency, simplicity, security or all of the above.

2. Simplify the checkout process.

Avoid turning users off with complicated checkout systems. Some businesses make the mistake of asking customers for so much information that they decide to buy their goods elsewhere. Your customer should know how much work is left to complete his or her order. A clean interface with a short pathway to purchase will keep customers from getting frustrated.

One simple way to cut the length of the checkout form is to allow a customer's ZIP code to autopopulate his town and state. You can even automatically migrate the sign-up information you collected into the checkout form. That way, the fields are already filled out; the buyer just needs to confirm them.

Related: How to Make Your First Ecommerce Sale (Infographic)

3. Add security measures.

A quick and easy transaction means nothing if it isn't secure. Identity theft is a growing concern -- more than 12 million Americans fall victim to it every year -- and consumers are more cautious than ever. In fact, 17 percent of mobile shoppers abandon their shopping carts due to security worries.

A good way to combat this is by using verification products and services that verify every transaction through a third party. These security measures ensure that all user information is encrypted and kept safe. Make sure your customers know that you encrypt their information. Customers who are nervous will look for security measures, and they'll be less likely to ditch their purchases if they believe their concerns have been addressed.

4. Send gentle reminders.

One of the advantages of an app is that you can send push notifications to your customers. Use this feature to remind them that they have items in their cart, but be wary of antagonizing them. Program the app to send alerts only to users who selected high-value items or spent several minutes browsing before filling their carts.

Push notifications can also be useful for providing purchase confirmations and tracking updates and informing customers of special offers.

5. Encourage sales with discounts.

Offer incentives to customers for making purchases through your app. Although discounts carry an initial cost, they can effectively grow your user base, boost customer satisfaction and jump-start your revenue if utilized correctly.

Food delivery startup Caviar did just that by waiving its delivery fees for first-time customers. The company also offers a $20 credit to users who share the app and get friends to make purchases.

These are five easy and inexpensive ways to improve your mobile experience and turn those abandoned shopping carts into sales. Listen to your customers from the get-go, and make sure they feel safe -- soon, they'll be clicking the "buy" button.

Related: 4 Strategies to Stop Shopping Cart Abandonment on Mobile