SEATTLE — Costco Wholesale Corp. said higher sales of discount items combined with a favorable tax rate helped push its profit up nearly 20 percent in its fourth quarter. Its shares rose more than 5 percent.

The wholesale club operator said it earned $354.7 million, or 73 cents per share, in the 16 weeks ended Aug. 28, up from $296.8 million, or 62 cents per share, a year ago. Revenue, including sales and membership fees, rose to $16.7 billion from $15.14 billion a year earlier.

A tax benefit and a lower tax rate — 28.9 percent versus 37 percent — boosted earnings for the latest quarter by 7 cents a share. Excluding those items, net income would have been $320.2 million, or 66 cents per share. That is 2 cents a share above the consensus forecast of analysts surveyed by Thomson Financial.

Costco, which operates 461 warehouses, including 339 in the U.S. and Puerto Rico, said net sales alone rose 10 percent to $16.36 billion from $14.83 billion for the quarter. Sales at warehouses open at least one year increased 7 percent from a year ago.

Costco Chief Financial Officer Richard Galanti said the company was hurt by higher gas prices, which reduced the company's profit margin on its own gasoline sales and also increased shipping costs.

Galanti didn't give specific guidance for the coming quarter and year, but he told analysts in a conference call that their consensus forecast is at the high end of the range. Analysts are forecasting earnings of 44 cents per share for the current first quarter, and $2.29 per share for the fiscal year ending next August.

Galanti said factors including uncertainty over gas prices make it hard to predict earnings at this point.

Costco said it expects to open 28 to 30 new stores in the U.S. in its current fiscal year, plus two or three new stores in Mexico. He also said the company may expand into a new country in its 2007 fiscal year. In addition to the United States, Costco operates in Canada, the United Kingdom, Taiwan, Korea, Japan and Mexico.

For the full fiscal year ended Aug. 28, net income rose to $1.06 billion, or $2.18 per share, from $882.4 million, or $1.85 per share, in the previous fiscal year. Excluding tax benefits and a charge for lease accounting, net income for fiscal 2005 would have been $998.3 million, or $2.04 per share, a 10 percent increase over the previous fiscal year.

Revenue including membership fees and sales rose to $52.94 billion from $48.11 billion.

Costco also said its board has authorized the repurchase of an additional $1 billion of common shares. This is on top of a previous authorization of $500 million, of which the company has spent $413 million to repurchase 9.2 million common shares at an average price of $44.87.

Costco shares rose $2.01, or 4.7 percent, to close at $44.92 yesterday on the Nasdaq Stock Market. Its shares have traded in a 52-week range of $39.48 to $50.46.