The top of the Roth IRA income band means “this is where it reaches zero.” But something odd happens in the $400 just below it — your income rises and the amount you may contribute stops falling. Then it disappears all at once, on the last dollar.
1. There is a $200 floor. When the computed figure drops below $200 it is raised back to $200. That is the rule in the IRS Publication 590-A worksheet.
2. So the end of the band is flat. Single and under 50, it is $200 all the way from $167,600 to $167,999 — and zero at $168,000.
3. Two IRS pages give different answers. The five steps on the short page have no floor — follow them and $167,999 produces $0.50.
What happens in the last $400
The rule itself is one line. In the words of Publication 590-A — “However, if the result is less than $200, enter $200.” The Roth side attaches a condition: “if the result is less than $200, you may contribute $200 if you are otherwise eligible.”
“Otherwise eligible” matters. The floor only operates while you are inside the band. Above the top of it you do not use the worksheet at all, and the answer is simply zero.
Enlarged, three things show at once.
- Steps — the $10 round-up means the line descends in flights rather than smoothly.
- A flat stretch — from $167,600 it stops at $200. Another $399 of income changes nothing.
- A cliff — $200 at $167,999, $0 at $168,000. One dollar of income costs $200.
Where the floor begins falls out of the arithmetic. The computed figure hits $200 at $200 × band width ÷ limit below the ceiling, so single and under 50 that is $200 × $15,000 ÷ $7,500 = $400 (our calculation) — hence $167,600.
Two IRS pages, two answers — an abbreviation, not a contradiction
The IRS page “Amount of Roth IRA contributions that you can make” compresses the arithmetic into five steps, the last of which ends “Subtract the result in (4) from the maximum contribution limit before this reduction. The result is your reduced contribution limit.” No rounding, no floor.
These are not pages contradicting each other — that one points readers to Publication 590-A for the detail. It is simply a short summary. But stop at the summary and you finish with a different number.
| Single, under 50, MAGI | The short five steps | Pub 590-A worksheet | Gap |
|---|---|---|---|
| $160,500 | $3,750 | $3,750 | none |
| $167,001 | $499.50 | $500 | $0.50 |
| $167,599 | $200.50 | $210 | $9.50 |
| $167,600 | $200.00 | $200 | none |
| $167,999 | $0.50 | $200 | $199.50 |
| $168,000 | $0 | $0 | none |
The widest gap is $199.50, at $167,999. Where the floor is not in play the gap never exceeds $9.50 (our calculation, walking every whole dollar in the band). The difference only matters in the last $400.
The floor is a different width in each band
$400 is the figure for a single filer under 50. A narrower band, or a higher limit, makes the floor shorter.
There is only one rule behind it: $200 × band width ÷ limit. So it is longer where the band is wide and shorter where the limit is high. Single and under 50 is the longest at $400.00; joint and over 50 the shortest at $232.56.
Joint and separate come out identical ($266.67) because both bands are $10,000 wide. Their starting points — $242,000 ~ $252,000 and $0 ~ $10,000 — could hardly be further apart, but the width of the floor has nothing to do with where the band starts.
The $10 round-up applies almost always
“Round up to the next $10” sounds like an occasional tidy-up. In practice it changes the figure at nearly every income.
Walking every whole dollar inside the single band — of 14,999 incomes, 14,250 are rounded up. Filing jointly it is 9,750 of 9,999 (our calculation). For a single filer the round-up does nothing only when the computed figure happens to be a multiple of $10, and since the limit $7,500 over a $15,000 band works out at $0.50 a dollar, that happens only when the income is a multiple of $20 — 749 of them in the whole band.
Put another way, this is not “a rounding error you can ignore” but “it almost always rounds in your favour.” Not by much — at most $9.50 for a single filer.
Questions this leaves
So at $167,999 may I really put in $200?
The worksheet’s answer is $200. The source does attach a condition — “you may contribute $200 if you are otherwise eligible” — meaning the other requirements, such as having taxable compensation, still have to be met. And this piece explains the rule; it is not telling you to do it. If your income sits at the very end of the band your final MAGI may land elsewhere when you file, and an excess contribution has its own correction procedure. Check with a tax professional.
Above $168,000, is even $200 out?
Yes. The floor only works inside the band. Above it you do not use the worksheet and the limit is zero. Publication 590-A is explicit that above the ceiling you “can’t make a Roth IRA contribution.”
Does the traditional deduction have the same floor?
It does. The wording differs slightly — the deduction worksheet says “enter $200,” the Roth side “you may contribute $200 if you are otherwise eligible.” The bands are different widths, so the floors are too. There is more in the traditional IRA deduction bands.
Why is the floor shorter at 50 and over?
Because the limit is $8,600, so more comes off for the same rise in income. Falling faster, it reaches $200 later. For a single filer the floor shrinks from $400.00 to $348.84 (our calculation).
How do I see where my income sits?
Put your MAGI into the IRA contribution and deduction calculator and it shows the position in the band, the figure before rounding, and whether the floor is holding it up.
Sources and where to check
IRS Publication 590-A — source for the $200 floor and the $10 round-up. Deduction worksheet: “If the result isn’t a multiple of $10, round it to the next highest multiple of $10. (For example, $611.40 is rounded to $620.) However, if the result is less than $200, enter $200.” Roth side: “if the result is less than $200, you may contribute $200 if you are otherwise eligible.” And above the ceiling, “can’t make a Roth IRA contribution.” (irs.gov)
IRS — Amount of Roth IRA contributions that you can make. Source for the five steps with no rounding and no floor, and one half of the abbreviation this piece describes. That page itself points readers to Publication 590-A for the detail. (irs.gov)
IRS news release — IR-2025-111 (based on Notice 2025-67). Source for the 2026 $7,500 and $8,600 limits and the three Roth income bands. (irs.gov)
Our own calculation — the $167,600 threshold, the six floor widths ($400.00, $348.84, $266.67, $232.56 among them), the $199.50 and $9.50 gaps between the two methods, and the round-up counts 14,250 of 14,999 and 9,750 of 9,999 are worked out from the figures above, walking every whole dollar of income in each band.
What we could not verify — the worksheet’s line numbers and the exact wording of each line. We confirmed the two rules in the body of Publication 590-A but could not open the table itself, so this piece cites no line numbers and describes only the rules. The order of the arithmetic is taken from the IRS five-step page.
As of August 2026, federal only. Not investment or tax advice. The two kinds of IRA are set out in the IRA guide, and the whole picture of the limits in 401(k) vs Roth IRA.
