How QuantCalc Models Retirement Taxes

Question 1

Does QuantCalc account for taxes in retirement projections?

Accepted Answer

Yes. QuantCalc's tax-aware mode models federal and 51-jurisdiction (50 states plus D.C.) income tax, Social Security taxation, Medicare IRMAA surcharges, long- and short-term capital gains, the Net Investment Income Tax, Required Minimum Distributions, Roth conversions, and the ACA premium-subsidy cliff, under 2026 law. The free mode runs a deterministic pre-tax baseline.

Question 2

How does QuantCalc handle Social Security taxation?

Accepted Answer

Social Security is included in taxable income according to the provisional-income rules, under which up to 85% of benefits can become taxable as other income rises. This captures the Social Security 'tax torpedo,' where an extra dollar of withdrawals or conversions can pull more of your benefit into taxable income.

Question 3

How does QuantCalc model Medicare IRMAA surcharges?

Accepted Answer

IRMAA (the income-related Medicare Part B and Part D premium surcharge) is modeled as a set of income cliffs based on modified AGI, reflecting the two-year lookback. Because a single dollar over a threshold adds a full surcharge tier, IRMAA is included in the year-by-year withdrawal-optimization cost so plans can avoid tipping over a bracket.

Question 4

Does QuantCalc model state income tax, and how accurately?

Accepted Answer

It models all 51 jurisdictions (50 states and D.C.) with each state's statutory treatment of retirement income — pension exclusions, Social Security exemptions, and capital-gains rules. Income is source-typed, so a pension, an IRA withdrawal, and Social Security are each taxed by the state according to that state's specific law rather than lumped together.

Question 5

How are capital gains and the NIIT handled?

Accepted Answer

Long-term capital gains are taxed at the preferential 0%, 15%, or 20% rates, stacked on top of ordinary income (so the applicable rate depends on total income), and the 3.8% Net Investment Income Tax applies once modified AGI clears its threshold. Only the appreciated portion of a taxable-account withdrawal is taxed; the return of cost basis is tax-free. The model recognizes the 0% long-term-gains bracket, where low ordinary income can let a retiree realize gains at zero tax.

Question 6

How does QuantCalc evaluate Roth conversions?

Accepted Answer

The optimizer weighs converting traditional balances to Roth in low-income years — 'filling' a tax bracket — against the future taxes those conversions avoid (lower RMDs, less Social Security taxation, and reduced IRMAA exposure later). It respects the ACA subsidy cliff and IRMAA thresholds while doing so, since a conversion that trips either can cost more than it saves.

Question 7

How are Required Minimum Distributions (RMDs) modeled?

Accepted Answer

RMDs are enforced from the SECURE 2.0 start age — 73 for those born 1951–1959 and 75 for those born 1960 or later — derived from the plan's calendar base year so conversion and IRMAA timing line up with the correct first-RMD year. A distribution shortfall incurs the 25% penalty.

Question 8

Does QuantCalc model the ACA subsidy cliff for early retirees?

Accepted Answer

Yes. For retirees under 65 on ACA marketplace coverage, it models the premium tax credit and the 400%-of-federal-poverty-level subsidy cliff, which returned for 2026 as the enhanced (cliff-free) subsidies expired. A pre-Medicare bridge can be optimized to keep modified AGI under the cliff while still funding spending and, where beneficial, doing Roth conversions.

Question 9

How are the standard deduction and the 2026 senior deductions handled?

Accepted Answer

Ordinary income is computed after the standard deduction for the filing status, plus two age-based additions once a filer turns 65: the additional standard deduction for the aged under IRC §63(f) (about $1,650 per qualifying married filer or $2,050 unmarried for 2026, granted per 65+ spouse on a joint return, with no income phase-out), and the OBBBA §70103 senior deduction ($6,000 per qualifying individual 65+, available for tax years 2025–2028, phasing out at 6% of modified AGI above $75,000 single / $150,000 joint, and unavailable to married-filing-separately filers).

Question 10

What is QuantCalc's approach to tax-efficient withdrawal sequencing?

Accepted Answer

Rather than a fixed rule like 'taxable first, then traditional, then Roth,' the optimizer computes the full tax cost of each candidate withdrawal mix each year — federal income tax, capital-gains tax, the NIIT, state tax, IRMAA, and any early-withdrawal penalty — and selects the mix with the lowest total. Over a multi-decade retirement this can differ substantially from a naive ordering.

Question 11

Which filing statuses does QuantCalc support?

Accepted Answer

Single, married-filing-jointly, and married-filing-separately, each with the correct federal brackets, standard deduction, senior deductions, and IRMAA schedule for that status.

Question 12

Is QuantCalc's output tax advice?

Accepted Answer

No. QuantCalc is a retirement-planning and education tool that models how taxes affect a plan under current law. It is not tax, legal, or investment advice. Tax law is complex and individual situations vary; consult a qualified tax professional or financial advisor before acting.

How QuantCalc Models Retirement Taxes

For financial advisors