WASHINGTON — Tax filing season will start on time this year despite a last-minute tax law passed by Congress, the IRS said Monday.

Taxpayers can start filing their 2014 tax returns on Jan. 20.

Congress passed a bill this month extending more than 50 tax breaks that had expired at the start of the year.

The new law extends the tax breaks through the end of the year, allowing taxpayers to claim them when they file their 2014 returns.

President Obama signed the bill into law on Dec. 19.

In previous years, last-minute tax laws passed by Congress have delayed tax filing season. But not this year, said IRS Commissioner John Koskinen.

“We have reviewed the late tax law changes and determined there was nothing preventing us from continuing our updating and testing of our systems,” Koskinen said. “Our employees will continue an aggressive schedule of testing and preparation of our systems during the next month to complete the final stages needed for the 2015 tax season.”

Each year, millions of taxpayers file returns during the first few weeks of tax season so they can get quick refunds.

In recent years, the IRS says it was able to issue most tax refunds within 21 days, if the returns were filed electronically. The IRS says that filing electronically is the fastest way to get a refund.

The IRS will process about 150 million individual tax returns. This year, refunds averaged about $2,800.