With the alternative minimum tax still unpatched for this year and estimated to spread to an additional 28 million households next tax season unless Congress acts to avert the fiscal cliff, recently released statistics from the Internal Revenue Service reveal that even the patched AMT hit millions more households in 2010 than in 2009.

The IRS’s Fall 2012 Statistics of Income Bulletin, released last week, describes the trends in individual income tax returns in 2010. Among them was a sharp increase in tax returns subject to the AMT. The number of returns with AMT liability increased 4.0 million from 3.8 million in 2009, a 5 percent spike.

“This marked the first year that the number of returns with AMT liability increased after two years of decreases,” wrote Justin Bryan.

After decreasing the previous year, following seven years of increases, AMT liability increased for 2010, with total AMT liability rising $4.9 billion, or 21.6 percent, to $27.5 billion.

In total, the IRS noted that nearly 143 million individual income tax returns were filed for tax year 2010, an increase of 1.7 percent from the 140.5 million returns filed for 2009. The adjusted gross income reported on these returns totaled $8.1 trillion, a 6.1 percent increase from the previous year.

Other articles in the quarterly SOI Bulletin cover topics such as partnership returns for 2010, nonprofit charitable organizations for 2009 and transactions between large foreign-owned domestic corporations and related foreign persons in 2008.

The bulletins are available for download at www.IRS.gov/taxstats.