There are about forty “tax dates” floating around the internet in January. Four of them have penalties behind them. Here’s the whole calendar, ranked by what actually happens if you miss.
The hard dates
| Date | What it is | Penalty if missed |
|---|---|---|
| Jan 31, 2026 | Employers must issue W-2s; brokers must issue 1099-Bs | None to you — chase the issuer, not the IRS |
| Apr 15, 2026 | 2025 return due; Q1 2026 estimated payment due | 5%/month to file, 0.5%/month to pay |
| Jun 15, 2026 | Q2 2026 estimated payment | 0.5%/month plus interest |
| Sep 15, 2026 | Q3 2026 estimated payment | 0.5%/month plus interest |
| Oct 15, 2026 | Extended 2025 returns due; Q4 payment window | Same as April |
| Jan 15, 2027 | Q4 2026 estimated payment | 0.5%/month plus interest |
The enforcement asymmetry almost everyone gets backwards
The failure-to-file penalty is 5% of unpaid tax per month (capped at 25%). The failure-to-pay penalty is 0.5% per month. Ten to one.
Translation: if April 15 arrives and you can’t pay, file anyway. Filing on time with a payment plan costs you the small penalty; sitting on an unfiled return costs you the big one. In eight busy seasons, every client who “waited until they had the money” paid multiples of what the filer-who-owed paid.
An extension extends your time to file. It has never, not once, extended your time to pay.
Extension trap number one
Form 4868 gets you to October 15. It does not move the April 15 payment obligation — the IRS estimates what you owe and expects that estimate by April. People who filed 4868 and paid nothing in April got billed interest plus the 0.5% penalty on the unpaid balance for six months. The extension is a filing tool, not a financing tool.
Extension trap number two
If you’re due a refund, there is no penalty for filing late — but the refund is forfeited if you don’t file within three years of the original due date (IRC §6514). For a 2022 refund, that clock ran out April 15, 2026. I had one client learn this in 2023 about a $2,140 refund from 2019. There is no appeal.
The 2026 numbers worth writing on the same calendar
- Standard deduction for 2026: $16,100 single, $32,200 married filing jointly (IRS Rev. Proc. inflation adjustments).
- 401(k) employee deferral: $24,500, plus $8,000 catch-up at 50+ (and the new $11,250 super catch-up for ages 60–63).
- IRA contribution: $7,500, or $8,500 at 50+.
- HSA: $4,400 self-only, $8,750 family.
Contribution deadlines for 401(k)s are December 31, 2026; for IRAs and HSAs, they’re tax-filing day — April 15, 2026 for the 2025 year.
What to do in January
Gather the documents now so April is a two-hour job, not a two-week panic. I wrote out my exact folder checklist here: The January Folder.