AutoZone, Inc. (AZO) shares are making big moves today after it posted better-than-expected fourth quarter earnings, helped by higher sales at established stores.

For the 16-weeks that ended August 29, Autozone said net sales grew 14 percent to $4.5 billion from $3.99 billion a year ago. Quarterly net income also rose 31 percent to $750 million, or $30.93 per share, compared with a year earlier profit of $565 million, or $22.59 per share.

Analysts were predicting earnings of $24.79 per share, and revenue of $4.15 billion.

Domestic same store sales, or those of stores open at least one year, increased 21.8 percent for the quarter. This is a key metric used to gauge a retailer’s success as it doesn’t include sales of stores that recently opened and closed during the year.

Total auto-part sales rose 14.2 percent, while total domestic commercial sales rose 10 percent. Sales from its other businesses – which include the diagnostic-software unit Alldata and e-commerce, went up 2.1 percent to $72.8 million.

For the quarter, gross margin dropped to 53.1 percent from 53.4 percent a year earlier, thanks lower merchandise margins driven primarily by a shift in mix.

Operating costs declined slightly to 34.5 percent from 35 percent of sales, because of leverage from higher sales growth, partially offset by $83.9 million of costs incurred in response to COVID-19.

Inventory rose 3.6 percent, driven by increased product placement and new stores, while inventory per store edged up by 9 thousand.

The company repurchased no shares in the latest period due to the uncertainty caused by the COVID-19 global pandemic.

Under its share repurchase program, which has $796 million remaining, the company bought 826,000 of its own stock for $930.9 million in the fiscal year.

At the end of its fiscal fourth quarter, the automotive parts company opened 49 new stores in the U.S., five in Brazil and opened eleven new stores in Mexico, lifting its store count to 6,549 locations.