MADISON, Wis. -- Consumers aren't taking advantage of the most wide-reaching tax credit in IRS history, officials said.

Anyone who has owned a phone between March 2003 and July 2006 is eligible for a one-time tax credit for the money that they have paid in federal excise taxes. It's a tax that, believe it or not, consumers have been paying to fund the Spanish-American War for years, WISC-TV reported.

The luxury tax on long distance phone use was enacted in 1898 as a way to get extra military funding from those who had phones, which at that time were the country's richest residents.

The tax was challenged in court last year, so now the U.S. Treasury and in turn, the IRS, will be giving the money back in the form of at least a $30 refund on taxes to the 160 million people eligible for it.

The problem is, the IRS said at least 30 percent of those eligible for the credit who have already filed this year aren't claiming it on their forms.

"A few people don't know about it, but the biggest reason is folks who are not required to file and are not going to file don't understand that this is a refundable credit, so they can get it too," said H&R Block district manager Patrice Gillespie.

To get the credit, consumers can take a standard deduction of $30 to $60 based on their filing status.

There is a special 1040EZ-T form for those who aren't required to file a regular return. Heavy long-distance users with their phone bills handy could calculate the taxes on a 8913 tax form and possibly get more back, WISC-TV reported.

Consumers who have already filed their taxes and didn't claim the credit still have time to file an amended tax return with the credit added, officials said.