To qualify, buyers must have a signed contract in hand by the deadline and must complete the deal by June 30.
The tax incentives - offered to both first-time buyers and some current homeowners - are fueling a strong spring selling season and helping home prices stabilize. Real estate agents hope the burst in activity, along with the lifting of general economic gloom, will propel the housing market for the rest of the year.
"It's been a great thing for us," said Andrew Dielmann, owner of Dielmann Sotheby's International Realty in St. Louis. "I would love to be a first-time homebuyer right now."
In Houston, transit mechanic Stan Henderson, 51, is buying his first home, a three-bedroom, $104,995 house from builder KB Home that is still under construction. Affordable prices and low mortgage rates were part of the draw, he said, but the tax credit "was the straw that stirred the drink."
Congress included the temporary tax credit in the $787 billion stimulus package signed into law a month after President Barack Obama took office last year. The idea was to bring the housing market back to life. Lawmakers, after intense lobbying from the real estate industry, agreed last fall to extend it until April 30.
Nearly 1.8 million households had used the credit as of mid-February at a cost of $12.6 billion, according to the Internal Revenue Service.
The government is offering buyers who haven't owned a home for three years a tax credit of 10 percent of the purchase price, up to $8,000. Single buyers with incomes above $145,000 and couples who make more than $245,000 are not eligible.
There is also a credit of 10 percent, up to a maximum of $6,500, for buyers who already own a home. To qualify, they have to have been homeowners for at least five years. The same income limits apply.
The incentives are juicing sales this spring. Sales of new homes surged 27 percent last month from a record low a month earlier; it was the biggest monthly increase in 47 years. Sales of previously occupied homes, meanwhile, were up nearly 7 percent in March and are expected to keep climbing.
After the tax credit is gone, though, the surge could be short-lived. Many analysts project sales will drop sharply in the second half of the year. Some expect prices to plunge as well, especially if mortgage rates rise and a wave of foreclosed homes hits the market.
Though the number of new foreclosures has come down a bit, it remains near record levels. Nearly 7.4 million borrowers, or 12 percent of all households with a mortgage, had missed payments or were in foreclosure as of March, according to Lender Processing Services Inc.
Still, the housing market seems finally to be regaining its footing after the worst downturn since the Depression.
Numerous government measures have helped. They include: the tax credit, the Obama administration's $75 billion foreclosure prevention plan, the Federal Reserve's $1.25 trillion program to drive down mortgage rates, and about $126 billion in taxpayer spending to stabilize mortgage finance companies Fannie Mae and Freddie Mac.
The Obama administration touts its efforts to stabilize the market as a success.
"For most Americans, their house is their most important financial asset," Treasury Secretary Timothy Geithner told lawmakers on Thursday. "As the financial crisis wreaked havoc on household wealth, the administration moved to protect this critical component of stability."
Skeptics say that these measures are an attempt to manipulate market forces and that they are leaving housing vulnerable to a dangerous double dip. And many economists say the main effect of the first-time buyer tax credit was to bring would-be homeowners into the market sooner.
"Most of the benefits went to people who would have bought a home anyway," said Patrick Newport, an economist at IHS Global Insight. He estimates that the tax credits will spark only 350,000 to 450,000 additional sales for 2009 and 2010 combined.
Tasha Brown, 29, of suburban Atlanta, is hoping to seal a deal by Friday. She had no intention of buying as house until a friend convinced her earlier this year that buying could be as affordable as renting. Then she learned about the tax credit.
"That was the thing that catapulted me," said Brown, an executive assistant.
She made an offer Monday on a foreclosed home, but the bank said it would take 10 days to approve the contract, which killed the deal. On Thursday, she was waiting to hear back from a seller on her offer of $141,000 for a home listed at $149,900.
"I haven't been sleeping for about two weeks," she said. But even if she doesn't get the credit, she won't stop looking. "I might be able to get something a lot better," she said. "It won't be a mad dash."