UPDATE 2-Costco to pay out $3 billion in special dividend

* Declares special dividend of $7 a share

* Several other companies plan payouts before year-end

* Costco shares up 5.4 percent in morning trade

Nov 28 (Reuters) - Costco Wholesale Corp on Wednesday said it will pay a special dividend totaling roughly $3 billion, the largest payout so far from any company ahead of a likely increase in the dividend tax.

The retailer also posted monthly same-store sales that beat analysts' expectations.

Shares of Costco, which charges a membership fee to let people shop at its stores for deals on everything from paper towels to diamond rings, rose 5.4 percent, or $5.10, to $101.68 in early trading.

Several companies have declared one-time cash dividends in recent days ahead of a likely increase in the dividend tax rate due to the so-called fiscal cliff - a combination of tax increases and spending cuts due to kick in at the beginning of 2013 if Congress and the White House cannot reach agreement on a plan to reduce the federal budget deficit.

Spirits company Brown-Forman Corp declared a $4-a-share special dividend on Tuesday, and casino developer Las Vegas Sands Corp, whose chairman is billionaire Republican donor Sheldon Adelson, announced a special dividend of $2.75 a share on Monday.

"We expect many cash-rich, stable operating companies to follow this trend, along with companies that have high insider ownership," Janney Capital Markets analyst David Strasser said.

Costco's dividend is worth nearly $3.07 billion, based on the number of shares outstanding at the end of the company's fiscal fourth quarter in early September.

The Las Vegas Sands dividend is worth about $2.27 billion, based on its outstanding shares in the third quarter that ended on Sept. 30.

LOTS OF CASH

Costco had cash and short-term investments of about $4.8 billion on Sept. 2, and the access to credit markets necessary to make a large payout.

Costco's cash balance before the special dividend "was truly excessive," said BMO Capital Markets analyst Karen Short, adding that the payout should not hurt future store openings.

"Our strong balance sheet and favorable access to the credit markets allow us to provide shareholders with this dividend," Costco Chief Financial Officer Richard Galanti said in a statement.

Costco, which raised its regular quarterly dividend to 27.5 cents per share earlier this year, plans to hold a conference call to discuss its special dividend later Wednesday.

On Nov. 19, Costco's bigger rival, Wal-Mart Stores Inc , moved its planned dividend to late December from early January to help shareholders avoid any increase in the tax rate.

Costco's special dividend will be paid on Dec. 18 to shareholders of record on Dec. 10.

November sales at Costco stores open at least a year rose 6 percent, helped by higher gasoline prices and dollar weakness, the company said. That compared with a forecast for 5.4 percent, according to Thomson Reuters data.

Excluding the effects of fuel and currency, Costco posted a November same-store sales increase of 5 percent. Net sales rose 9 percent to $8.15 billion in the four weeks to Nov. 25.