$14,007 difference over 30 yearsFor one couple (both 60, $2M, 60/40, $80,000 a year to spend after tax), QuantCalc's 51-state planner study found a median 30-year income-tax bill (federal + state + IRMAA) of $184,926 in Colorado and $198,933 in Arizona — Colorado is the cheaper state by $14,007.
Colorado vs Arizona at a glance
| Factor | Colorado | Arizona |
|---|---|---|
| State income tax | 4.40% top | 2.50% top |
| Taxes Social Security | Yes | No |
| Taxes 401(k)/IRA | Yes | Yes |
| State estate/inheritance tax | No | No |
| Tax on $100k withdrawal | $196/yr | $1,290/yr |
| Retirement-friendliness | moderate | friendly |
| 30-yr median income tax, federal + state + IRMAA (MC) | $184,926 | $198,933 |
| 30-yr state income tax (MC) | $20,278 | $36,841 |
| 30-yr success rate (MC) | 83.73% | 83.27% |
| Median balance at 90 (MC) | $2,113,337 | $2,073,138 |
The income-tax difference, year by year
The simplest way to see the gap: take a married couple, both 65, whose only income is a $100,000 IRA withdrawal split evenly between them. On that withdrawal Colorado collects $196 in state income tax and Arizona collects $1,290 — a difference of $1,094 every year. Both figures are QuantCalc's state tax engine run on the couple's whole 2026 return in each state, so each state's own brackets, deductions, retirement-income exclusions and credits apply. One flat bracket, with a Social Security and pension subtraction that turns fully exempt at 65. One flat bracket since the 2023 reform, exempts Social Security.
Over a 30-year retirement, QuantCalc's 51-state planner study (one couple, identical portfolio and after-tax spending in both states, only the state changes; every year priced by the planner's federal and state tax engines) puts the median income-tax difference at $14,007.
Beyond income tax
State income tax is only part of the retirement-cost picture. When comparing Colorado and Arizona, also weigh:
- Property tax — a tax-free-income state can still have high property tax; factor your home value.
- Sales tax — affects every dollar you spend, not just income.
- Estate / inheritance tax — Colorado: none; Arizona: none. Matters for larger estates.
- Roth conversion cost — converting in the lower-income-tax state of the two cuts the state tax on each converted dollar. See conversion-tax scenarios.
See Colorado vs Arizona on your full plan
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Compare all states →Converting to Roth before or after the move? See the Roth Conversion Planner.
Compare other states
Deep-dive either state: Colorado retirement tax guide · Arizona retirement tax guide. Or see the full 50-state comparison and the 51-state Monte Carlo study.
FAQ
Is Colorado or Arizona better for retirement taxes?
On income tax, Colorado is the lighter-tax state. In QuantCalc's 51-state planner study, one couple (both 60, $2M, $80,000 a year to spend after tax) pays a median $184,926 of federal and state income tax and IRMAA over 30 years in Colorado versus $198,933 in the other — a $14,007 difference on identical income and spending.
Does Colorado tax Social Security and 401(k) withdrawals?
Colorado taxes Social Security benefits and taxes 401(k)/traditional IRA distributions at the state level. One flat bracket, with a Social Security and pension subtraction that turns fully exempt at 65.
Does Arizona tax Social Security and 401(k) withdrawals?
Arizona does not tax Social Security benefits and taxes 401(k)/traditional IRA distributions at the state level. One flat bracket since the 2023 reform, exempts Social Security.
How much would moving from Colorado to Arizona save on retirement taxes?
For a married couple, both 65, whose only income is a $100,000 IRA withdrawal split evenly between them, the state income tax is $196 in Colorado versus $1,290 in Arizona — $1,094 per year of difference. Over 30 years, the planner study's median income-tax gap was $14,007. Don't forget property tax, sales tax, and estate tax also differ — see the table above.
Last updated 2026-10-28. State tax data 2026 (Tax Foundation + state DoR); the withdrawal figures are QuantCalc's state tax engine. Monte Carlo figures from the QuantCalc 51-state planner study (v2026.3, re-run 2026-10-12, CC-BY-4.0): one couple, both 60, $2M, 60/40, $80,000 a year to spend after tax, in each state. Educational only, not tax advice.