To calculate Social Security income for a mortgage, lenders start with the gross monthly benefit shown on your award letter, then increase the nontaxable portion by a set percentage so it can be compared to taxable wage income. That increase is called grossing up, and it runs 15% on FHA loans and typically 25% on conventional loans when you aren’t required to file a federal tax return. The resulting figure, not your actual deposit, is what the underwriter enters into the loan application.
Why Lenders Gross Up Nontaxable Benefits
Mortgage qualification runs on gross income. A worker earning $3,000 a month in wages takes home less after federal tax; a retiree receiving $3,000 a month in nontaxable Social Security keeps every dollar. To put both borrowers on equal footing, lenders raise the recognized value of the nontaxable benefit by roughly what the tax would have been. The gross-up doesn’t put more money in your account. It changes the number the underwriting system uses to measure what you can afford.
The gross-up only applies to benefits that aren’t taxed. If part of your Social Security was taxed on your most recent return, the lender grosses up only the untaxed share and leaves the taxed share alone. Many retirees whose only income is Social Security fall below the IRS thresholds and owe no federal tax on their benefits at all, which is the scenario where grossing up delivers the most.1Internal Revenue Service. Publication 915 (2025), Social Security and Equivalent Railroad Retirement Benefits
Conventional Loans: 25% Gross-Up
Fannie Mae’s Selling Guide lets the lender develop an adjusted gross income for nontaxable benefits by adding back the tax the borrower would otherwise owe.2Fannie Mae. General Income Information Most conventional lenders apply 25% for borrowers who aren’t required to file a federal return. If you did file and paid at a lower effective rate, the lender uses that actual rate instead.
A $2,000 nontaxable monthly benefit at 25% becomes $2,500 for qualifying purposes ($2,000 × 1.25). That extra $500 shifts your debt-to-income ratio.
FHA Loans: 15% Gross-Up
FHA is more conservative. Under the Single Family Housing Policy Handbook, the gross-up cannot exceed the greater of 15% or the borrower’s actual tax rate from the prior year. If you weren’t required to file, 15% is the ceiling.3Department of Housing and Urban Development. FHA Single Family Housing Policy Handbook
Same $2,000 benefit, FHA rules, no tax filing: $2,000 × 1.15 = $2,300. If you filed and your effective rate was 22%, the FHA lender uses 22%, and the grossed-up figure becomes $2,440. FHA doesn’t default to 25% the way conventional lending typically does.
The Calculation Step by Step
Take a borrower with a $1,600 gross monthly retirement benefit and no other income.
- Start with the gross benefit. Use the figure on your award letter, before any Medicare or other deductions. Here, $1,600.
- Determine taxability. Annual benefits of $19,200 produce combined income of $9,600 (half of the benefit plus other income). That’s below the $25,000 single-filer threshold, so the full benefit is nontaxable.4Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
- Apply the gross-up. Conventional, no tax filing: $1,600 × 1.25 = $2,000. FHA, no tax filing: $1,600 × 1.15 = $1,840.
- Enter the result on the application. The grossed-up figure goes into the income section of the Uniform Residential Loan Application, and the automated underwriting system uses it to compute debt-to-income.
When Only Part of Your Benefits Are Taxable
Higher combined income makes up to 50% and eventually up to 85% of benefits taxable. The lender splits the benefit and grosses up only the nontaxable side. For a $2,000 monthly benefit where $1,000 is nontaxable, a conventional lender grosses up the untaxed half ($1,000 × 1.25 = $1,250) and leaves the taxed half at $1,000, producing $2,250 of qualifying income.
Adjustments to the Starting Number
Medicare Premiums
The standard Medicare Part B premium for 2026 is $202.90 per month and is usually withheld from your check before deposit.5Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles Lenders generally use the gross benefit from the award letter, not the smaller amount that lands in your bank account. Expect the underwriter to reconcile the gap by comparing your award letter to your deposits.
Working While Collecting Benefits
If you claim retirement benefits before full retirement age and keep working, the earnings test can shrink your check. For 2026, the SSA withholds $1 for every $2 earned above $24,480; in the year you reach full retirement age, the threshold rises to $65,160 and the reduction drops to $1 for every $3.6Social Security Administration. Receiving Benefits While Working If your benefit is currently reduced by the earnings test, lenders use the reduced amount, not the original award figure. Wages count as a separate income stream with their own documentation.
Federal Offsets and Garnishments
Defaulted federal student loans, unpaid taxes, and other federal debts can trigger a Treasury Offset that reduces your benefit before it reaches you.7Consumer Financial Protection Bureau. Issue Spotlight: Social Security Offsets and Defaulted Student Loans Some lenders will use the reduced figure. For garnished alimony under FHA rules, if the payment wasn’t already subtracted from the gross benefit, the lender adds it back as a recurring debt in the DTI calculation.3Department of Housing and Urban Development. FHA Single Family Housing Policy Handbook Disclose any offset upfront; the discrepancy between award letter and deposit will surface in underwriting.
Documents That Support the Number
The lender verifies your calculation with paperwork from the SSA and your own files:
- A Benefit Verification Letter (sometimes called a proof of income letter or award letter) confirming benefit type, gross monthly amount, and start date. You can request one through your my Social Security account.8Social Security Administration. How Can I Get a Benefit Verification Letter
- Your most recent SSA-1099, which shows prior-year benefits and lets the underwriter check whether any portion was taxed. SSI recipients don’t receive a 1099 because SSI isn’t taxable.9Social Security Administration. Get Tax Form (1099/1042S)
- One or two years of federal tax returns, used to identify your tax bracket and any taxable benefits.
- Two months of bank statements showing the direct deposits, matched against the award letter.
Fannie Mae also accepts the SSA-1099 or signed federal returns as standalone documentation of retirement or disability benefits when paired with proof of current receipt.10Fannie Mae. Selling Guide Announcement SEL-2022-09
Three-Year Continuity
Regardless of benefit type, the payments must be expected to continue for at least three years from the note date.2Fannie Mae. General Income Information Retirement benefits meet this automatically. SSDI and SSI require evidence that no scheduled termination or medical review falls within that window. Survivor benefits paid on behalf of a child count only if the child is young enough for payments to continue three more years past closing, since payments stop at 18 (or 19 if still a full-time high school student).11Social Security Administration. Becoming an Adult A birth certificate is standard proof.
Why the Gross-Up Moves the Needle
Everything above feeds one number: the debt-to-income ratio. Fannie Mae caps DTI at 36% for manually underwritten conventional loans, with room up to 45% for stronger files and up to 50% through Desktop Underwriter.12Fannie Mae. Debt-to-Income Ratios FHA can go higher with compensating factors.
Consider a borrower with a $1,600 nontaxable benefit and $800 in total monthly debts including the proposed housing payment. Using the raw benefit, the DTI is 50%, right at the conventional automated limit. Apply a 25% gross-up and qualifying income becomes $2,000, dropping the DTI to 40%. Same money in the mailbox, very different outcome in underwriting.