Chipotle Mexican Grill ( CMG) reported a decline in second-quarter earnings against year-earlier results that were boosted by a tax benefit, but the burrito chain's profit margins and sales both improved.

Chipotle, the McDonald's ( MCD) spinoff whose shares were devoured on Wall Street after its IPO in January, said Monday that it earned $10.8 million, or 33 cents a share, in the second quarter. Analysts polled by Thomson First Call expected earnings of 25 cents a share.

A year earlier, Chipotle's earnings were $25.7 million, or 98 cents a share. But excluding the one-time tax benefit that inflated last year's results by 77 cents a share, Chipotle's earnings rose more than 50%.

On an operating basis, Chipotle said its profits increased 70% to $15.9 million for the quarter, while its operating margins increased 180 basis points to 21.7%.

"Our profitability stems from continuing strong comparable restaurant sales, successful new restaurant openings, and favorable commodity costs," said Chipotle in a press release.

The company's total revenue for the quarter rose 31% to $204.9 million, surpassing analysts' target of $199.6 million. Its comps, measuring sales at restaurants open at least a year, rose 14.5% amid an increase in the number of customers visiting the chain.

For the year, Chipotle expects its comps to rise "in the low double-digits." On a quarterly basis, it expects its comp increases to decline as the year progresses due to tougher comparisons with last year's results. Over the longer term, its management "remains comfortable with Chipotle's ability to grow income from operations at an annual rate of approximately 25%."

Chipotle opened 14 company-owned restaurants during the quarter, including 12 restaurants in existing markets and two restaurants in new markets. For the year, it plans to open 80 to 90 new locations.

Shares of Chipotle recently were down $1.65, or 3.1%, to $50.85 in after-hours trading, after they rose 4.7% during the regular session.