I always max out my HSA each year and somehow I came up short just over $100 and I thus made a deposit to my HSA from my checking account for that amount (post tax of course) to count towards my 2016 limits. I filled in f1040 Line 25 with that amount and it got me wondering if there's anything analogous for other forms of pretax accounts I can likewise contribute to after the fact?

For instance my retirement account at work contributes pretax, and we have some commuter benefits as well. Is there a way on the 1040 to flesh out some contributions to something along those lines? I like to do this sort of thing when I wind up owing more taxes come this time of year. Seems like Line 32 could be something to take advantage of if I set up my own account and use it for these purposes, but that's assuming I can set on up in 2017 and have it count for 2016 contributions, which I think is allowed up to the cutoff date of Tax Day right?

  • Is your question specifically about the 401(k)? Are there any other types of accounts that you are wondering about?
    – Ben Miller
    Commented Mar 11, 2017 at 3:29
  • Could be 401k, I'm really interested in the idea of optionally topping off at the end of the year to avoid having any taxes due. I'll be logging into my 401k probably tomorrow and seeing if there's an equivalent make a deposit that's counted as a 2016 contribution much like I did with my HSA.
    – jxramos
    Commented Mar 11, 2017 at 4:19
  • FYI, there is nothing wrong with having to send in a little money with your tax return. All it means is that you had access to more of your money all year long. If you end up with a big refund, it means that you gave the government an interest-free loan.
    – Ben Miller
    Commented Mar 11, 2017 at 4:44
  • 2
    Of course, there is nothing wrong with trying to save extra on your taxes, either.
    – Ben Miller
    Commented Mar 11, 2017 at 5:22
  • @BenMiller I think you'd agree that your overall tax burden is more important that your net tax due (or refunded). You can pay too much in tax and still get a refund.
    – D Stanley
    Commented Mar 12, 2017 at 3:39

1 Answer 1


For a 401(k), only contributions that you make for the current tax year through payroll deduction are tax-deductible. Those contributions are subtracted off of your income for your W-2 Box 1 income amount. If you make a manual contribution to your 401(k) outside of that, it is not tax deductible, and there is nowhere on your Form 1040 to deduct it.

Your commuter benefits are also paid for out of payroll deduction and deducted on your W-2, so this is not an option, either.

You could contribute to a traditional IRA for last year up to your tax return deadline, and deduct the amount on Form 1040 Line 32. However, because you have access to a retirement plan at work, your IRA contribution is only tax deductible if your income is below certain limits.

  • I think this inspires a second question, what tax benefits can only be taken advantage of through payroll deductions?
    – jxramos
    Commented Mar 12, 2017 at 2:55

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