Retirement tax planner: installment vs. lump sum
If you’re selling your home in or near retirement, spreading the gain over a seller-financed installment sale can change how much of it is taxed each year, and whether it pushes your income over thresholds for the Net Investment Income Tax or Medicare premiums. Enter your numbers to see a year-by-year comparison against selling for a lump sum.
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Educational information, not legal, tax or financial advice.
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Your estimate
$0
difference in total after-tax cash
Lump sum
$0
total after-tax cash
- Total tax
- $0
- Years with NIIT
- 0
- Years flagged for IRMAA
- n/a
Installment
$0
total after-tax cash, over 0 years
- Total tax
- $0
- Years with NIIT
- 0
- Years flagged for IRMAA
- n/a
- Your gain
- $0
- Section 121 exclusion
- $0
- Taxable gain
- $0
- NIIT threshold (MAGI)
- $0
- Your IRMAA threshold (MAGI)
- $0
NIIT and IRMAA flags explained: a year is flagged for NIIT when your estimated modified adjusted gross income (other income + recognized gain + interest) is over the NIIT threshold shown above; the tax applies to the smaller of your investment income or the amount over that threshold. A year is flagged for IRMAA when that same MAGI is over the threshold you entered. Leaving the IRMAA field blank skips that flag entirely.
Year-by-year schedule
View the table
| Year | Installment: principal | Installment: interest | Installment: gain | Installment: tax | Installment: NIIT | Installment: after-tax cash | Lump sum: after-tax cash (cumulative) |
|---|
How this calculator works
- Your gain. Sale price minus selling costs, minus your cost basis, with the Section 121 exclusion applied first (up to $250,000, or $500,000 married filing jointly, if you’re eligible).
- Lump sum. Tax on the whole taxable gain in year one; the after-tax proceeds are then assumed to earn your reinvestment rate each year, with that interest taxed at your ordinary income rate, so the two scenarios can be compared like-for-like.
- Installment sale. Each year, the share of principal you receive that represents taxable gain follows the gross profit ratio (taxable gain ÷ sale price). Interest is taxed as ordinary income every year the note is outstanding.
- NIIT and IRMAA each year. Estimated MAGI is your other income plus that year’s recognized gain and interest. NIIT applies at 3.8% on the lesser of your investment income or the excess over the statutory threshold. IRMAA is simply flagged when MAGI is over the threshold you entered.
The math comes from the same engine Clavesta uses in its app, and reconciles exactly with thehome sale tax calculator at the same flat rates.
Important caveats
- Flat rates only — no tax brackets, state income tax, or depreciation recapture.
- IRMAA tiers change yearly; you supply the threshold, this tool doesn’t look one up.
- Doesn’t model Social Security taxability, Medicare Part A, or required minimum distributions.
- A note rate below the IRS applicable federal rate can trigger imputed interest.
- Year 1 includes the down payment and the first 12 monthly payments, not a calendar year.
Frequently asked questions
Why would spreading the sale over several years help in retirement?
If part of your gain is taxable, recognizing it over several years instead of all at once can keep more of each year’s income under the Net Investment Income Tax (NIIT) threshold, or under an IRMAA threshold you set for Medicare premiums. If your tax rate would be identical every year, the total tax is roughly the same either way — you just pay it as you’re paid, which this tool shows.
What is the Net Investment Income Tax (NIIT)?
An extra 3.8% federal tax on investment income — including taxable gain and the note’s interest — when your modified adjusted gross income (MAGI) is above $200,000 (single) or $250,000 (married filing jointly). These statutory thresholds aren’t adjusted for inflation. The NIIT applies to the smaller of your investment income or the amount your MAGI exceeds the threshold.
What is IRMAA, and why does this tool ask for a threshold?
IRMAA (Income-Related Monthly Adjustment Amount) is a surcharge Medicare adds to Part B and Part D premiums when your MAGI from two years earlier is above an income tier. Those tiers change yearly and depend on filing status, so this tool asks you to enter the threshold that applies to you (or leave it blank to skip the flag) rather than guessing a number that could be wrong for your year.
Is the CSV download something I can just hand to my CPA?
It’s a starting point: the year-by-year numbers this calculator produced from your inputs, including the assumptions used. It is not a tax return, Form 6252, or a substitute for your CPA’s own calculation with your full financial picture, but it can save time by laying out the numbers in one place.
Does this account for tax brackets?
No. You enter one flat capital gains rate and one flat ordinary income rate, and the calculator applies them directly with no bracket math. Real tax brackets can split a single year’s gain or interest across more than one rate, so treat this as a simplified estimate, not a tax return.
What does the lump sum column assume?
That you sell for cash, pay tax on the gain in year one, and invest the after-tax proceeds at the reinvestment rate you enter, with the interest earned taxed each year at your ordinary income rate. It’s meant for a like-for-like comparison with the installment schedule, not investment advice about where to put the money.
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