The Dow Jones industrial average fell 85 points to 12,925 shortly after the opening bell Monday.
The Standard & Poor's 500 index lost eight points to 1,401 and the Nasdaq composite was also off eight points at 2,959.
Shoppers flooded stores in record numbers over the weekend, according to the National Retail Federation. The organization said 247 million shoppers visited stores and shopping websites during the Thanksgiving holiday, up 9.2 percent from last year.
On Monday, however, the National Economic Council and the Council of Economic Advisers said that a sudden increase in taxes for middle-income taxpayers could reduce consumer spending next year by nearly $200 billion.