CHICAGO — Holiday shoppers who enjoyed the convenience of fulfilling wish lists with a simple click of the “buy” button are learning this week that the return process for online purchases can still be a hassle.

E-commerce purchases can be made with little effort, but shoppers say the returns are almost never as straightforward.

Lauren O’Connor would rather not have made the trip to a post office Tuesday morning. But she needed to return a dog bed and coat she bought online at Lands’ End for her new puppy. Lands’ End doesn’t have a store near her home, so carting her online purchase back to a bricks-and-mortar location, as some shoppers do, wasn’t an option.

That’s how she found herself waiting with an unwieldy square cardboard box while struggling to find a pen to address the package, all without forfeiting her place in a growing line.

“It’s just a big hassle,” she said.

Dealing with returns is a pain for retailers too, and one that’s only getting bigger, said Chris Zubel, a managing director at real estate services firm CBRE.

Online sales are growing, and shoppers are more likely to return items bought over the internet, Zubel said. That’s because on-screen images don’t always match what the item looks like in person, and consumers buying apparel often order the same item in multiple sizes or colors, intending to send all but one version back.

Estimates of the return rate for online purchases range from 15 to 30 percent, depending on the type of item purchased and who you ask, compared with 8 percent for all U.S. merchandise sales, according to a 2015 report from the National Retail Federation and software company The Retail Equation. The problem is worse over the holidays, when shoppers buy more gifts, apparently with mixed success. Overall merchandise return rates rise about 2 percent in November and December.

United Parcel Service sees a bump in shipping volumes throughout the month of January as customers return unwanted gifts, order items in exchange and spend gift cards, said spokesman Matthew O’Connor. But the first week of January is UPS’ busiest period for e-commerce returns, tracked using the pre-printed shipping labels some retailers provide to make returns easier for customers.

The early-January flurry of activity is good news for shipping companies like UPS, which expects to ship about 5.8 million returns during the first week in January 2017, up from about 5 million the year before, O’Connor said. It’s not such great news for the customers making extra trips to ship return packages, or retailers that have to figure out what to do with extra merchandise that comes back.

Most returns that were purchased online get returned to brick-and-mortar stores, as long as the retailer has a physical store that is convenient for the customer. Unless the returned item is unusually bulky or something not typically stocked in the store, that’s often the best outcome for the retailer, which can put the item back on a shelf and try to sell the customer something else.