In 2008, first-time home buyers were eligible to receive a tax-credit. The government referred to it as something similar to an interest free loan. Americans could take advantage of this on the condition that starting about now, they would pay back the loan over a 15 year period (if they took the maximum amount of $7,500). When the government gave out these loans, it was 'creating' money and injecting it into the economy. This increased the money supply and expanded the circular flow. Now the government wants their money back. Since households are paying these loans back in taxes, money is being leaked from the economy and the circular flow will shrink. If people have to pay more a year in taxes, they may have to cut spending in other areas of their lives. If spending drives the economy, this won't bode well for trying to propel the economy up into a recovery period.
Click here to read the article that discusses paying back the credit.