The amount of 401K contributions on your W-2 is not included in your Box 1 amount. That is how you get the tax deduction, so unless you are also lowering your Box 1 amount, you may not see a change. A change in your W-2 401K may change your Saver's Credit if you qualify for the credit. If you saw no change when you changed the amount, revisit the Saver's credit interview as this is where you would see your tax bill lowered. If you don't qualify for the Saver's Credit, you won't see a change. https://ttlc.intuit.com/replies/3301263