Pennsylvania taxpayers will leave as much as $31 million of tax refunds on the table unless they file 2010 tax returns, and those missing out are the people who could most use it - the working poor.

While taxpayers focus on the deadline for 2013 taxes, another deadline approaches: the deadline for revising or filing 2010 taxes.

Most of the refunds have not been claimed because some taxpayers have not filed their 2010 taxes. The IRS doesn't go out and find them, said Democratic U.S. Sen. Bob Casey, who wanted to spread the word among Pennsylvanians.

Many who have unclaimed refunds are low earners who are not required to file taxes, but can.

About 1 million Americans don't file their taxes at all, mostly part-time workers and students. Also, those who moved or worked only part of the year may not think they are not obliged to file taxes. But by not filing or forgetting to file, they forgo a tax refund. They may even be entitled to tuition tax credits or earned income tax credits.

"I want to make sure that unclaimed refunds from 2010 go to the taxpayers, or else they will get returned to the treasury," Casey said.

That $31 million is payable to an estimated 37,400 non-filers in Pennsylvania. The average refund is $614.

A single person with a child earning less than $15,700 in 2010 isn't required to file taxes, but probably should, said Jennifer A. Jenkins, an IRS spokesperson. Money deducted from the pay check of a low wage workers often exceeds their actual tax liability. If the employee doesn't file a tax return, they will have ended up overpaying the federal government and won't get that money back.

Nationwide, the IRS has about $760 million of uncollected tax refunds for the 2010 tax year.