I contribute to a 401k plan, how do I show that amount on my taxes or am I supposed to?

When you get your W-2, you will see your taxable wages in Box 1. Compare this with the Social Security Wages in Box 3. The difference between those two boxes includes your 401k contribution, which appears in Box 12, with Code D.

You document your contribution to your 401k by entering all your W-2 information into your tax software. If you do a manual return, you just use Box 1 for wages, it already has the 401k contribution subtracted. No separate entry for your 401k contributions appears in the tax return.

You pay no current income tax on the amount in Box 12. All earnings from your contributions are also tax-deferred until you withdraw them at retirement.

In addition, if your Box 1 income is below certain limits, you may get a Savers Credit on contributions to your 401k. You appear to be above the threshold ($25,000), unless you have deferred enough to get below $25,000.

So, many tax benefits.

Like tonal said, you won't have to deduct the 401(k) contributions on your tax return because they're not included in your wages on your W-2. Your employer will have already done the deducting for you. Just enter the amount of wages shown on your W-2 on your tax return and that's it.

You don't show it on your taxes. You get the tax break automatically, since the amount you contributed isn't included as taxable income on your W-2.

These deferred wages (commonly referred to as elective deferrals) are not subject to income tax withholding at the time of deferral, and they are not reflected on your Form 1040 since they were not included in the taxable wages on your Form W-2. However, they are included as wages subject to social security, Medicare, and federal unemployment taxes.

More info:

http://www.irs.gov/taxtopics/tc424.html

Make sure and see if you qualify for the Saver's Credit....