The Internal Revenue Service has opened its 21st season of electronic filing. The agency has sent reminders to taxpayers saying e-file remains the best way to get fast refunds and ensure accurate tax returns, particularly following several changes in the tax law. A number of tax deductions and credits for were extended for 2011 and 2012.

To date, the IRS says it's processed over one-billion returns through e-files. In 2010, nearly 100 million people - or 70-percent of taxpayers - used IRS e-file. IRS commissioners anticipate that more tax return preparers will be using e-file this year.

They anticipate starting to process tax returns impacted by December's tax law changes by mid-February.

Even with the delay, the IRS says e-file remains the fastest option. It will take less than two weeks to process an e-filed return, but as many as four to six weeks to process a paper return.