How Area Median Income drives every affordable housing program.

What AMI actually means

Area Median Income (AMI) is the midpoint of family income in a given geographic area, as estimated by the U.S. Department of Housing and Urban Development (HUD). Half of family households in the area earn more; half earn less. HUD publishes these estimates annually for every metropolitan statistical area and non-metropolitan county in the United States.

In affordable housing finance, AMI is almost never used at face value. Programs reference percentages of AMI to define their target populations:

• Extremely Low Income (ELI): at or below 30% of AMI
• Very Low Income (VLI): at or below 50% of AMI
• LIHTC target: 50% or 60% of AMI (and post-2018, anywhere from 20% to 80% under income averaging)
• Low Income: at or below 80% of AMI

These percentage bands then determine income eligibility for tenants and the maximum gross rent a unit can charge. AMI is the bedrock; everything else is derivative.

How HUD calculates AMI

HUD's methodology has been stable since 2009, when the agency moved to the American Community Survey (ACS) as the primary data source. The calculation has several stages:

1. Source data. HUD pulls five-year ACS estimates of family income for every metropolitan statistical area (MSA) and non-metropolitan county. ACS surveys roughly 3.5 million households annually.
2. Trending forward. Because ACS data lags by two-plus years, HUD applies a national Consumer Price Index (CPI-U) trend factor to bring the figures to the current fiscal year.
3. Geographic definitions. HUD applies its own Fair Market Rent (FMR) area definitions, which sometimes split or combine OMB MSAs to better reflect local rental markets. Some HMFA (HUD Metropolitan Fair Market Rent Area) sub-areas differ from OMB MSAs.
4. Income limit derivation. HUD then publishes income limits at different AMI percentages, with adjustments for household size from 1 to 8 persons. The 4-person household at 100% AMI is the anchor figure; other household sizes scale from there.
5. High and low cost adjustments. Where the local cost of housing materially exceeds what the area's median income would support, HUD applies a high-cost-area adjustment. Similar adjustments exist for very low cost areas.

The result is published as the Multifamily Tax Subsidy Project (MTSP) Income Limits table for LIHTC and bond-financed properties, and as a separate HUD Income Limits table for HUD programs like Section 8 and HOME. The MTSP and HUD tables agree most of the time, but not always — HERA hold-harmless rules (discussed below) can keep the MTSP figures from declining even when the underlying area median falls.

Household-size adjustments

Income limits are published for households of 1 through 8 persons. The adjustment factors HUD uses (relative to 4-person median income at 100% AMI):

For household sizes larger than 8, the limit increases 8% per additional person, applied to the 4-person base.

From income limit to maximum LIHTC rent

The LIHTC maximum gross rent (Section 42(g)(2)) is calculated as 30% of the applicable income limit, adjusted by household size based on bedroom count using an imputed-occupancy convention. The bedroom-to-household-size mapping for LIHTC rent calculations:

The 1.5-persons-per-bedroom convention applies to all bedroom sizes. For fractional household sizes (1.5, 4.5), HUD interpolates between the published household-size income limits.

"Gross rent" includes tenant-paid utilities (a utility allowance based on local averages is subtracted to determine the maximum net rent the owner can charge). The 30% multiplier reflects HUD's longstanding affordability threshold: a household is "cost burdened" if it pays more than 30% of income for housing.

Income averaging (HERA 2018, post-2018 fixes)

The Consolidated Appropriations Act of 2018 added a third LIHTC minimum set-aside test under Section 42(g)(1)(C). Properties can now elect the income averaging set-aside, under which:

• At least 40% of units must be both rent-restricted and occupied by tenants with incomes at or below the unit's designated AMI level
• Individual units may be designated at any 10% increment from 20% AMI to 80% AMI
• The average of all designated units across the building cannot exceed 60% of AMI
• The same rent and income restrictions apply to each unit based on its individual designation

Income averaging has been popular for mixed-income deals because it allows higher-AMI units (e.g., 80%) that command closer-to-market rents, cross-subsidizing deeper-affordability units (e.g., 30% or 40%) that otherwise would not pencil.

HOTMA changes (2023 onward)

The Housing Opportunity Through Modernization Act of 2016 (HOTMA) included several provisions affecting how income is counted for affordable housing programs. The implementing rules took years to finalize. Key effective dates:

• HUD final rule (24 CFR 5): Published February 14, 2023; effective for HUD programs January 1, 2024 (with a phased compliance period extending into 2025)
• IRS LIHTC alignment: Treasury has not formally adopted all HOTMA provisions for LIHTC compliance, but most state allocating agencies have updated their tenant income certification procedures to match HOTMA conventions

Major HOTMA changes that affect LIHTC and HOME tenant qualification:

• Asset limits: Households with net assets above $100,000 (indexed) are generally ineligible for HUD assistance, with exceptions for the elderly and disabled. LIHTC has no statutory asset limit, but states may impose one.
• Real property exclusion: Households cannot own real property suitable for occupancy as a residence and meet eligibility, with limited exceptions
• Excluded income items: Expanded list of excluded income (some retirement account distributions, certain gifts under a threshold)
• Student income treatment: Revised rules for counting income from full-time students
• Streamlined re-examinations: For elderly and disabled households on fixed income, triennial re-certifications replace annual
• Safe harbors: Owners can use IRS Form 4506-T tax transcripts as a safe harbor for income verification

Hold-harmless rules (HERA)

Under Section 3009 of the Housing and Economic Recovery Act of 2008 (HERA), LIHTC and tax-exempt bond properties enjoy a hold-harmless rule: the applicable MTSP income and rent limits cannot decrease from one year to the next for a building that was placed in service in or before a prior year. This protects existing properties from rent reductions when the underlying area median falls (which can happen during recessions or due to ACS data revisions).

The hold-harmless applies per building, locked at the highest MTSP figure published in or before the building's placed-in-service year. New buildings placed in service in the current year always use the current year's published limits — they have no prior limits to compare to.

Effective dates and the annual publication cycle

HUD typically publishes the new year's income limits in late April or early May. The exact effective dates vary slightly by program:

Property owners have a 45-day implementation window after MTSP publication to apply the new limits. For tenant income determinations in progress at publication, the prior year's limits may continue to apply through the certification.

How different programs use AMI differently

Not all programs use the same AMI figures or the same percentage bands:

When stacking programs in one deal, you may need to comply with multiple sets of income and rent limits simultaneously. The strictest limit governs each unit.

Practitioner checklist

1. Use the MTSP table, not the HUD Income Limits table, for LIHTC unit qualification
2. Apply the imputed-household-size convention (1.5 persons per bedroom) when calculating maximum rents
3. Apply hold-harmless: existing buildings use the higher of current MTSP and prior MTSP at PIS year
4. Check whether your state QAP imposes deeper-AMI targeting than the federal 60% maximum (most do for at least some units)
5. Confirm your state's adoption of HOTMA conventions for LIHTC tenant certifications
6. Don't forget utility allowances — they reduce the maximum collectable rent below the gross rent ceiling
7. Verify the placed-in-service year of each building before applying limits; mixing PIS years across one project is a common error