I believe the answer the OP is seeking is as such, putting additional money into your 401k does indeed reduce your overall tax liability, however you will not get a bigger refund because your employer is simply withholding less taxes from each of your paychecks. As others have stated, your primary goal should be to reduce your overall tax liability, not increasing your refund. That said, if you want to increase your refund there are two ways to do it, one is to have your employer withold more from each of your paychecks, or increase your tax deductions that the employer does not account for (ie home mortgage interest, dependents, business expenses etc).