How is the marginal rate of tax calculated for someone who has no income but only capital gains?
If by “marginal rate of tax” you mean “top marginal rate of tax,” the answer has to be the highest rate assessed on the capital gain net income shown on a return. Income is income, regardless of whether it is ordinary income or capital gain income. One might argue for an “effective” rate of tax, which is likely lower than the “top marginal rate of tax” because of the availability of standard (or itemized) deductions and personal exemptions, etc. Divide the total tax by total income to get the effective rate, and where the top marginal tax rate on a capital-gains-only return might be 20%, the effective rate will likely be lower.
