I do have our daughter living with me full-time since the separation. I didn't know this was an option! What exactly qualifies as "separated" though? We don't have any legal separation agreement, just living in different places for about 8 months now.

For the IRS, being "separated" means you and your spouse didn't live in the same household during the last 6 months of the tax year. You don't need a formal separation agreement for tax purposes. Since your daughter lives with you full-time and you've been living separately for 8 months, you likely qualify for Head of Household status. This gives you a higher standard deduction and better tax rates than Married Filing Separately. You'll also remain eligible for certain credits that you lose with MFS. Definitely look into this option in TurboTax - there should be a section where you can check if you qualify for HOH status!

Your ex will be the one in trouble, not you. If you were legally married on December 31 of the tax year, neither of you can file as Single - that's tax fraud on their part. The IRS will likely catch this when they match Social Security numbers and may audit your ex, but you're fine since you filed correctly as MFS.

That's a really good point I hadn't considered. I did file pretty early (mid-February) because I usually get a refund. I'm going to log into my brokerage account right now and see if they issued a corrected 1099-B that I missed. If they did, would I need to file an amended return or just respond to the notice with the updated information?

You typically don't need to file an amended return in this case. The response to the notice effectively serves as your correction. In your response letter, you should explain that you filed with the original information provided by your brokerage, and include copies of both the original and corrected 1099-B forms. Make sure to clearly reconcile the differences between what you reported and what the corrected form shows. The IRS mostly wants to see that you can account for the discrepancy and that you're not trying to hide income. They're generally reasonable when the error originated with the brokerage rather than you.

Online response is definitely better when available! But you still need to scan and upload all your supporting documents. I did mine online last year and still had to upload about 20 pages of stock transaction records. But processing time was only about 3 weeks versus the 2+ months it took when I mailed in a response the previous year.

You make a good point about still needing to provide all the documentation. I should have been clearer. The main advantage isn't reducing what you need to submit, but rather the processing time and confirmation. When you submit online, you get an immediate confirmation that they received your response, which gives peace of mind compared to wondering if your mail got lost. The other major advantage is that online responses typically get processed in the order received, while paper responses can get shuffled into various processing backlogs. This is especially important when responding to a notice with a deadline.

How do you prove mileage if you get audited? I've been taking pics of my odometer before and after shifts... is that enough?

A mileage log is your best bet. You don't need to take pics of your odometer (though it doesn't hurt), but you should record the date, starting location, ending location, purpose of the trip, and total miles driven. There are free apps that can help track this automatically. The IRS mostly wants to see that you have a consistent record-keeping system, not just estimates after the fact. Even a simple spreadsheet or notebook works as long as you update it regularly. If you claim a ton of miles with zero documentation, that's when audit flags can pop up.

While technically all income should be reported, the practical reality is that the IRS is not going to come after you for a few dollars in tax on $38. DoorDash won't issue any tax documents for this amount. That said, it's generally best to develop good tax habits from the start. If this is your only income, you likely wouldn't even need to file. If you have other income requiring you to file anyway, including the $38 is the right thing to do, but realistically, the impact on your tax bill will be minimal and the chances of issues arising from omitting it are extremely low.

1 That sounds stressful! Did you end up having to pay penalties or just the corrected tax amount? I'm trying to avoid any issues with my ESPP reporting this year.

14 I had to pay the additional tax plus about $120 in interest since it had been nearly 8 months since the filing deadline. Fortunately no major penalties since they determined it was an honest mistake and not deliberate underreporting. The most annoying part was having to fill out an amended return and providing all the documentation showing which transactions were which. The whole process took about 3 months to resolve. Definitely worth getting it right the first time if you can!

20 In my experience, tax software doesn't always get ESPP transactions right, especially with disqualifying dispositions. Last year TurboTax didn't connect the dots between my W2 ESPPDD and the 1099 for the same shares. I had to manually override the cost basis. It's always good to understand what's happening rather than trusting the software completely.

Is that safe harbor thing calculated for the whole year or for each quarter separately? I always thought I just had to hit 100% of last year's taxes by the end of the year.