Guides
Every calculator here answers one question with a number. These explain the rule behind it, and where people get caught.
Who the rule reaches, which wage figure decides it, and why changing jobs resets the test. The four details that produce confident wrong answers.
The extra amount anyone 50 or over may contribute, how it sits on top of the ordinary limit, and why the figure depends on your plan type and your age.
The provision that pays back employer match you missed by contributing unevenly, and how to tell whether your plan has one.
Why hitting the annual limit early can cost you employer match, what it is worth, and the cases where doing it anyway is defensible.
Four calendar years with a higher catch-up limit, both edges of the window, and what it is worth across the whole span.
The Roth catch-up rule removes the pre-tax option. If your plan has no Roth option either, the contribution cannot be made at all.
Your employer withheld exactly what the regulations require, and you still owe money at filing. This explains why.
What your employer sells on vest day, what it is meant to cover, and why the proceeds routinely miss the real tax bill.
Extra withholding, a quarterly estimated payment, or paying at filing. What each one does about a vest that was under-withheld.