Washingtonians who itemize their income tax returns but wait until the last minute to file will soon get a reminder, if any is needed, that Congress can procrastinate, too.

When the temporary deduction for state and local sales taxes was about to expire last year, federal lawmakers took so long to approve a two-year extension that the tax-return instructions had already gone to the printers without any explanation for how to claim it. That means those who want information about itemizing sales tax payments on their 2006 federal tax return will need to obtain a separate form, IRS Publication 600.

After Congress took away the ability to deduct sales taxes in 1986, Washington and a handful of other states, found themselves at a disadvantage compared with states that impose state income taxes, the only substantial state tax that could still be listed as a deduction against the federal tax liability. That’s the way it stood for nearly two decades before a provision was made that allowed taxpayers in states with a sales tax but no income tax to receive similar treatment. But only temporarily.

Unfortunately, the last-second fix Congress came up with last year is also temporary. It’s good only through the 2007 tax year, meaning the waiting game could be repeated in the waning months of next year.

To her credit, Washington Sen. Maria Cantwell, a Democrat, has joined with Texas Sen. Kay Bailey Hutchison, a Republican, to provide for a state sales tax deduction in the Senate’s 2008 Budget Resolution. That’s not the same as putting a permanent deduction into law, however, although Cantwell says it sends a signal that permanence is now a congressional priority.

Maybe, but early in 2006, members of Washington’s congressional delegation were confident that extending the about-to-expire deduction would be little more than a formality. Then, there they were with two outs in the bottom of the ninth inning before they pulled it out. And now, there are Washington’s taxpayers, scratching their heads over how and where on their returns to enter the appropriate information.

It’s vital, as a matter of fairness, that Cantwell and the rest of the state’s congressional delegation show their constituents an energetic commitment to the measure, starting now.

Most states in the nation rely heavily on their income taxes for state revenues, and their residents are able to soften the blow by deducting what they pay the state from what they owe the IRS. Washington relies mostly on the sales tax, which accounts for almost half the taxes it collects, and this state’s residents are entitled to the same courtesy.

And the figure is about to go up, following passage of legislation that positions Washington and its cities and counties to begin collecting sales taxes on more catalog and Internet purchases – an estimated $25.7 million more in 2009, according to the Washington Research Council.

Approval of the so-called Streamlined Sales Tax Project was a prudent step by the state. Among other things, it removes the competitive advantage out-of-state businesses now have over the state’s own retailers. But it will increase the amount of sales taxes paid in this state, which is that much more reason for Congress to act promptly on the deductibility issue.