CHICAGO — The parent of Sears and Kmart has apologized for canceling “a couple thousand” online layaway contracts during the final shopping days before Christmas and vowed that the company is “working hard to make things right.”

“We are in the process of contacting our customers and members who have received inadvertent cancellation notices for their online layaway contracts,” Sears Holdings said in a blog post Wednesday. “This issue is specific to online layaway contracts for ship to home and does not impact in-store layaways.”

Angry customers took to Kmart’s Facebook page during the past week to complain that they received cancellation notices for online layaway orders for which they had already paid, leaving them fighting for refunds and scrambling to get new gifts at the last minute. The notices from Kmart stated that the items were out of stock.

The layaway process entails holding items for people who wish to pay in installments to ensure they are available. It isn’t clear why items weren’t held.

In its apology, Sears Holdings said it has processed refunds for canceled items and that customers will receive the refunds soon, if they haven’t already. The retailer said it is searching its inventory and stores for items that its system identified as out of stock, and if it finds them it will provide them to the customers for free and ship at no cost.

Kmart, which has made layaway a central part of its marketing message, has suffered a long stretch of sales declines along with Sears.