Side-by-side tax comparison between Idaho (5.3% top rate, flat) and South Dakota (no income tax). See which state lets you keep more at every salary level, and how cost of living changes the picture.
South Dakota has no state income tax, while Idaho uses a flat system with rates of 5.3% flat. On a $100K salary, this creates a state tax difference of $5,300/year that South Dakota residents simply don’t pay.
Idaho’s flat 5.3% rate means the gap scales linearly with income. At $200K, you’d save $10,600 by being in South Dakota instead.
South Dakota wins at 10 out of 10 salary levels tested. The advantage is consistent and significant across the income spectrum.
| Salary | Idaho | South Dakota | Difference | Winner |
|---|---|---|---|---|
| $40K | $32,200 | $34,320 | +$2,120 | South Dakota |
| $50K | $39,705 | $42,355 | +$2,650 | South Dakota |
| $60K | $47,210 | $50,390 | +$3,180 | South Dakota |
| $75K | $57,563 | $61,538 | +$3,975 | South Dakota |
| $100K | $73,825 | $79,125 | +$5,300 | South Dakota |
| $120K | $86,835 | $93,195 | +$6,360 | South Dakota |
| $150K | $105,801 | $113,751 | +$7,950 | South Dakota |
| $200K | $138,287 | $148,887 | +$10,600 | South Dakota |
| $250K | $170,014 | $183,264 | +$13,250 | South Dakota |
| $300K | $199,429 | $215,329 | +$15,900 | South Dakota |
Take-home pay only tells part of the story. Idaho has a cost of living index of 95 while South Dakota is at 92 (national average = 100).
With similar costs of living (95 vs 92), the tax difference is the primary factor. What you see in raw take-home pay is essentially what you get in purchasing power: $77,711 in Idaho vs $86,005 in South Dakota.
For a single earner at $100K filing jointly, take-home becomes $79,410 in Idaho and $84,710 in South Dakota \u2014 a difference of $5,300. The gap remains similar regardless of filing status.
On paper, moving from Idaho to South Dakota would save $5,300/year on a $100K salary, or $26,500 over 5 years. But relocation involves real costs: moving expenses, potentially buying/selling a home, changing jobs, and adjusting to a new community.
With an annual savings of $5,300, the tax difference alone is significant enough to justify a move for many people — especially if career opportunities are comparable. At higher salaries, the savings grow even larger: a $200K earner would save $10,600/year.