Filing tax extension but not sure how much to pay - how to calculate taxes owed when you haven't filed yet?

You're in a common situation! When filing an extension, you do need to make your best estimate of taxes owed, but it doesn't have to be perfect. Here's what I recommend: Use last year's tax information and this year's estimated income to make a rough calculation. Since your husband's income increased and you mentioned he typically owes, you'll want to be conservative in your estimate. If you have your final paystubs from 2024, those can help you estimate your W-2 information - they usually show year-to-date tax withholding. For newly married couples, sometimes the "marriage penalty" can kick in when both spouses have similar high incomes. If your husband's income jumped substantially, that's something to consider. The penalty for underpayment is basically an interest charge (currently around 8% annually) on the amount underpaid. If you pay at least 90% of what you end up owing, you can avoid the penalty altogether. And yes, you can absolutely overpay and get a refund later when you file your complete return!

I was in this exact situation last year! I discovered this tool called taxr.ai (https://taxr.ai) that was super helpful for estimating what I would owe before I had all my documents. You just upload what you have, and it helps calculate your estimated liability. I was missing a 1099 and one W-2, but I knew approximately what I'd earned. The tool helped me figure out a safe amount to pay with my extension. They have this smart calculator that factors in your withholding from paystubs and previous year's returns. Ended up paying about $1200 with my extension, and when I finally filed, I owed $950, so I got a small refund.

I was really skeptical about using taxr.ai when I first heard about it, but I gave it a try last month when I realized I wouldn't have all my documents before the deadline. I'm amazed at how well it worked! I have rental properties and a fairly complex tax situation, but the system helped me calculate a pretty accurate estimate. What impressed me was how it handled my missing K-1 forms - I just put in what I expected based on last year with a slight increase, and it factored that into my calculations. I paid what they recommended with my extension, and it was actually a bit more than I ended up owing. Getting that small refund was way better than dealing with penalties. Definitely worth checking out if you're filing an extension.

I've been through the extension nightmare before and totally get your stress! After spending HOURS trying to get through to the IRS for guidance last year, I finally found Claimyr (https://claimyr.com). Their service got me connected to an actual IRS agent in about 15 minutes instead of the usual endless hold times. I explained my situation about filing an extension without all my documents, and the agent walked me through how to make a reasonable estimate based on my last paystub of the year. They even helped me understand which form to use for the extension payment. You can see how it works in this video: https://youtu.be/_kiP6q8DX5c Seriously saved my sanity during tax season. The IRS agent actually gave me some tips about how to avoid penalties that I never would have known otherwise.

I have to admit I was completely wrong about Claimyr. After my skeptical comment, I decided to try it when I got desperate trying to figure out my extension payment. I had called the IRS directly 5 times over 3 days and either got disconnected or couldn't stay on hold any longer. Used the Claimyr service and no joke, I was talking to an IRS representative in under 20 minutes. The agent helped me calculate a safe estimate based on my last year's return and this year's pay stubs. Turns out I was overthinking it - they said paying 100% of last year's tax liability would protect me from any underpayment penalties as long as my AGI was under $150k. Since we're newly married too, the agent gave me specific advice about how that affects the safe harbor rules. Completely worth it just for the peace of mind.

One important thing no one mentioned yet - if you're expecting a significant income increase like your husband had, make sure you're looking at the safe harbor rules correctly. If your AGI is over $150,000, you need to pay 110% of your previous year's tax liability (not just 100%) to avoid penalties. Also, filing status matters here. Since you were both single last year and married this year, you'd need to calculate 110% of your COMBINED previous year tax liability. This is exactly why I use a CPA even though it costs more. They handle all this headache and help me sleep at night!

Just want to add something I learned the hard way - if you do end up owing a penalty for underpayment, make sure to use Form 2210 to calculate it yourself rather than waiting for the IRS to do it. Especially if you had uneven income during the year. The standard calculation assumes you earned income evenly throughout the year, which can result in a higher penalty if you earned more toward the end of the year. Form 2210 lets you show when you actually earned the income so the penalty is calculated fairly.