Side-by-side tax comparison between Idaho (5.3% top rate, flat) and Washington (no income tax). See which state lets you keep more at every salary level, and how cost of living changes the picture.
Washington 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 Washington 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 Washington instead.
Washington wins at 10 out of 10 salary levels tested. The advantage is consistent and significant across the income spectrum.
| Salary | Idaho | Washington | Difference | Winner |
|---|---|---|---|---|
| $40K | $32,200 | $34,320 | +$2,120 | Washington |
| $50K | $39,705 | $42,355 | +$2,650 | Washington |
| $60K | $47,210 | $50,390 | +$3,180 | Washington |
| $75K | $57,563 | $61,538 | +$3,975 | Washington |
| $100K | $73,825 | $79,125 | +$5,300 | Washington |
| $120K | $86,835 | $93,195 | +$6,360 | Washington |
| $150K | $105,801 | $113,751 | +$7,950 | Washington |
| $200K | $138,287 | $148,887 | +$10,600 | Washington |
| $250K | $170,014 | $183,264 | +$13,250 | Washington |
| $300K | $199,429 | $215,329 | +$15,900 | Washington |
Take-home pay only tells part of the story. Idaho has a cost of living index of 95 while Washington is at 110 (national average = 100).
The cost of living gap is moderate. After adjustment, $100K has purchasing power of $77,711 in Idaho vs $71,932 in Washington. However, Idaho actually provides better purchasing power despite Washington’s take-home advantage.
For a single earner at $100K filing jointly, take-home becomes $79,410 in Idaho and $84,710 in Washington \u2014 a difference of $5,300. The gap remains similar regardless of filing status.
On paper, moving from Idaho to Washington 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.