I'm in a similar situation.
First, a 529 plan can be use for "qualifying" international schools. There are 336 for 2015, which includes many well known schools but also excludes many schools, especially lower level or vocational schools and schools in non-English speaking countries.
I ran 3 scenarios to see what the impact would be if you invested $3000 a year for 14 years in something tracking the S&P 500 Index:
- Invest in Vanguard's 500 Index Portfolio in their 529 plan and withdraw it for qualifying use.
- Invest in the same 529, but withdraw it for non-educational use.
- Invest in Vanguard's S&P 500 Index Fund in a taxable account
For each of these scenarios, I considered 3 cases: a state with 0% income tax, a state with the median income tax rate of 6% for the 25% tax bracket, and California with an income tax rate of 9.3% for the 25% tax bracket.
California has an addition 2.5% penalty on unqualified distributions. Additionally, tax deductions taken on contributions that are part of unqualified distributions will be viewed as income and that portion of the distribution will be taxed as such at the state level.
Vanguard's 500 Index Portfolio has a 10 year average return of 7.63%. Vanguard's S&P 500 Index fund has a 10 year average return of 7.89% before tax and 7.53% after taxes on distributions.
Scenario 1
Use a 529 as intended:
No State Tax 6% State Tax California
------------ ------------ ------------
Investment Return Rate: 7.63% 7.63% 7.63%
State Income Tax Rate: 0.00% 6.00% 9.30%
Total Contributions: $45,000.00 $45,000.00 $45,000.00
Gains: $31,148.36 $31,148.36 $31,148.36
Value After 14 Years: $76,148.36 $76,148.36 $76,148.36
State Income Tax Deductions: $ 0.00 $ 2,700.00 $ 4,185.00
Total Value Including Deductions: $76,148.36 $78,848.36 $80,333.36
Taxes and penalties on withdrawal:
Federal Income Tax @ 25%: $ 0.00 $ 0.00 $ 0.00
Federal Capital Gains @ 15%: $ 0.00 $ 0.00 $ 0.00
State Income Tax @ State Rate: $ 0.00 $ 0.00 $ 0.00
Federal Penalty @ 10%: $ 0.00 $ 0.00 $ 0.00
State Penalty @ State Rate: $ 0.00 $ 0.00 $ 0.00
------------------------------------ ------------ ------------ ------------
Total after taxes and penalties: $76,148.36 $78,848.36 $80,333.36
Effective return rate: 7.63% 8.06% 8.29%
Scenario 2
Use a 529 but do not use as intended:
No State Tax 6% State Tax California
------------ ------------ ------------
Investment Return Rate: 7.63% 7.63% 7.63%
State Income Tax Rate: 0.00% 6.00% 9.30%
Total Contributions: $45,000.00 $45,000.00 $45,000.00
Gains: $31,148.36 $31,148.36 $31,148.36
Value After 14 Years: $76,148.36 $76,148.36 $76,148.36
State Income Tax Deductions: $ 0.00 $ 2,700.00 $ 4,185.00
Total Value Including Deductions: $76,148.36 $78,848.36 $80,333.36
Taxes and penalties on withdrawal:
Federal Income Tax @ 25%: $ 7,787.09 $ 7,787.09 $ 7,787.09
Federal Capital Gains @ 15%: $ 0.00 $ 0.00 $ 0.00
State Income Tax @ State Rate: $ 0.00 $ 4,568.90 $ 7,081.80
Federal Penalty @ 10%: $ 3,114.84 $ 3,114.84 $ 3,114.84
State Penalty @ State Rate: $ 0.00 $ 0.00 $ 778.71
------------------------------------ ------------ ------------ ------------
Total after taxes and penalties: $65,246.44 $63,377.54 $62,349.64
Effective return rate: 5.70% 5.33% 5.13%
Scenario 3
Invest in a S&P 500 Index fund in a taxable account:
No State Tax 6% State Tax California
------------ ------------ ------------
Investment Return Rate: 7.53% 7.53% 7.53%
State Income Tax Rate: 0.00% 6.00% 9.30%
Total Contributions: $45,000.00 $45,000.00 $45,000.00
Gains: $30,537.35 $30,537.35 $30,537.35
Value After 14 Years: $75,537.35 $75,537.35 $75,537.35
State Income Tax Deductions: $ 0.00 $ 0.00 $ 0.00
Total Value Including Deductions: $75,537.35 $75,537.35 $75,537.35
Taxes and penalties on withdrawal:
Federal Income Tax @ 25%: $ 0.00 $ 0.00 $ 0.00
Federal Capital Gains @ 15%: $ 4580.60 $ 4580.60 $ 4580.60
State Income Tax @ State Rate: $ 0.00 $ 1,832.24 $ 2,839.97
Federal Penalty @ 10%: $ 0.00 $ 0.00 $ 0.00
State Penalty @ State Rate: $ 0.00 $ 0.00 $ 0.00
------------------------------------ ------------ ------------ ------------
Total after taxes and penalties: $70,956.75 $69,124.51 $68,116.78
Effective return rate: 6.75% 6.42% 6.24%
Conclusion
Given similar investment options, using a 529 fund for something other than education is much worse than having an investment in a mutual fund in a taxable account, but there's also a clear advantage to using a 529 if you know with certainty you can use it for qualified expenses. Both the benefits for correct use of a 529 and the penalties for incorrect use increase with state tax rates.
I live in a state with no income tax so the taxable mutual fund option is closer to the middle between correct and incorrect use of a 529. I am leaning towards the investment in a taxable account.