Thank you so much for explaining this! I never considered that my W-4 might need updating with the new 401k contributions. Should I ask my HR department about adjusting my withholding, or is that something I need to figure out on my own?

You should start by using the IRS Tax Withholding Estimator on their website - it will help you figure out what adjustments you need to make. It's pretty user-friendly and walks you through everything step by step. After you know what changes you need, then talk to your HR department. They'll have the forms you need to update your withholding. Just explain that you want to adjust your W-4 because of the 401k contributions and income changes. They deal with this stuff all the time and should be able to help you complete the form correctly.

This is exactly what my financial advisor told me! She said big refunds are basically giving the government an interest-free loan all year. I adjusted my withholding too and have been putting the extra $200/paycheck into a high-yield savings account. By the time tax season came around, I had actually earned interest on that money instead of letting the IRS hold it for free.

But wait - I thought Roth contributions were tax deductible? Are you saying they're not?

You're confusing Roth contributions with traditional retirement contributions. Roth contributions (which is what code AA represents) are made with after-tax money, meaning you pay tax on that income now. The benefit is that when you withdraw the money in retirement, including all the growth, it comes out tax-free. Traditional 401(k) contributions (which would be code D in Box 12) are tax-deductible now, but you pay taxes when you withdraw the money in retirement.

For the AA codes (Roth 401k contributions), the amount is already INCLUDED in your Box 1 wages because Roth contributions are made with after-tax dollars. If you had traditional 401k contributions (which would be code D in Box 12), those would already be EXCLUDED from your Box 1 wages because they're pre-tax. You don't need to make any adjustments either way - the Box 1 amount is already correct.

Thank you! That makes sense. So basically the Box 1 amount is what I should be using for my tax return, and all these codes in Box 12 are just additional information that I don't need to do anything with.

That's a really good point about the percentage seeming high. I hadn't thought about that. Do you have any recommendations for a good app or system to track mileage? I'm terrible about remembering to log trips.

MileIQ and Everlance are both great apps for tracking mileage automatically. They run in the background on your phone and detect when you're driving. At the end of each trip, you just swipe right for business or left for personal. Super simple and creates IRS-ready reports. For your situation, I'd also recommend taking photos of receipts for any supplies you purchase during these trips and noting any additional rental-related stops. The more documentation you have connecting these trips directly to your rental business, the better position you'll be in if questioned.

The rental property expenses would go on Schedule E as rental expenses, not as unreimbursed employee expenses. The 2018 tax law changes (TCJA) didn't eliminate deductions for legitimate rental property expenses. Since they're managing their own rental property, the vehicle expenses related to that rental activity are deductible on Schedule E regardless of their W2 status for their day jobs. The key is properly allocating and documenting what portion of vehicle use is specifically for the rental activities versus personal use.

Thanks for the info about TaxSlayer and IRS Direct Pay! I was wondering about making the payments online instead of mailing them. Does the Direct Pay system give you a confirmation that you can save for your records?

Yes, the IRS Direct Pay system provides a confirmation number immediately after your payment processes. You can print this confirmation page or save it as a PDF. I recommend doing both and keeping a folder (digital or physical) for each tax year with all your payment confirmations. They also send a confirmation email if you provide your email address during the payment process. I personally save these emails in a dedicated tax folder in my email account for easy reference later.

This is such an important point. I had the same thing happen in New York. Paid all my federal estimated taxes but completely forgot about state requirements. Ended up with almost $200 in penalties even though my actual state tax bill wasn't that high.

Thanks for mentioning this! Does the deduction for half the SE tax reduce the amount of SE tax I pay, or just my income tax? And do I need a separate form for that or is it part of the regular 1040?

The deduction for half of your SE tax doesn't reduce the SE tax itself, but it does reduce your income tax. It's considered an "adjustment to income" (sometimes called an "above-the-line deduction"), which means you get this benefit even if you take the standard deduction rather than itemizing. You don't need a separate form for this deduction. When you complete Schedule SE to calculate your self-employment tax, the form will automatically calculate the deduction amount. This amount then transfers to Schedule 1 of your Form 1040 as an adjustment to income. Tax software handles this transfer automatically, making it pretty seamless.

If your W-2 wages already hit the Social Security limit ($168,600 for 2024), you'd only pay the Medicare portion (2.9%) on your self-employment income. If your W-2 is below the limit, you pay the full SE tax on your net self-employment income, but only up to the point where your combined income hits that limit. Either way, you still calculate it on Schedule SE.