Does filing a tax extension give me more time to pay what I owe?

No — and this trips people up every year. An extension (Form 4868) gives you until October 15 to file your return, but it does not extend the deadline to pay. Any tax you owe is still due by the original April deadline, and interest plus a late-payment penalty accrue on unpaid balances after that date. So if you file an extension but owe money, you should estimate your liability and pay it by April to avoid charges. The extension simply protects you from the much larger failure-to-file penalty while you gather documents or wait on a K-1. It's automatic and free if you submit on time. Bottom line: extend to file, but pay your best estimate by the April deadline. If you can't pay in full, pay what you can and look into an IRS payment plan.