Don't leave money behind -- or stint your retirement-saving potential. By David Muhlbaum, Senior Online Editor April 4, 2011 If you’ve already filed your 2010 tax return, good for you. We have some guidance on how to put your tax refund to good use (if you had one coming).But the April 18 date isn’t just for your return — it’s also a significant deadline for a couple of other items: Claiming an Old Refund If you have money due you for the tax year 2007, April 18 is your last chance to claim it. How many people leave money on the table at the IRS? The service estimates about 1.1 million people did -- and that the total available is more than $1.1 billion. Much of this money might have been earned by people who didn't make enough to need to file a tax return -- but who had money withheld from their paycheck anyway. Summer earnings by a pool-watching teenager, for example. Advertisement Also: If you've been digging into past years' taxes and are planning to amend for tax year 2007 and want to get more money back, that April 18 deadline applies as well for filing your 1040-X. Funding Your Retirement The Individual Retirement Account is a powerful tool to save on taxes and get your retirement funded. Have we said that before? Yes? Okay, fine. April 18 is the deadline for putting in your 2010 contribution to an IRA. You can contribute up to $5,000 (or $6,000 if you were age 50 or older at the end of last year). It might be tax-deductible, too, even if you already participate in a retirement plan through an employer. For more on the merits and how-tos of this retirement vehicle, read Fund an IRA, Cut Your Taxes.