Difficult Development Area (DDA)

What Is a Difficult Development Area?

A difficult development area (DDA) is a place where affordable rental housing is especially hard to finance because land, construction, and utility costs are high relative to local incomes. The U.S. Department of Housing and Urban Development (HUD) designates DDAs each year for the Low-Income Housing Tax Credit (LIHTC). Projects located in one can earn a larger credit through the basis boost.

How It Works

The statute sets no formula, so HUD uses rents as a stand-in for development costs. For the 2026 list, HUD:

1. Computed a ratio for each area. The numerator was a modified two-bedroom Small Area Fair Market Rent for each metropolitan ZIP Code area, or a two-bedroom county Fair Market Rent outside metro areas. The denominator was a monthly LIHTC rent limit calculated from HUD’s four-person very low-income limit.
2. Ranked the areas from highest ratio to lowest, separately for metro and nonmetro areas, and dropped ZIP areas with fewer than 100 residents.
3. Selected from the top until the designated areas reached 20% of the total metro population, and separately 20% of the nonmetro population, leaving out areas already designated as QCTs.

Because metro DDAs are drawn at the ZIP Code level, they are often called Small Area DDAs (SADDAs). HUD’s lookup tool labels them Small Difficult Development Areas (SDDAs). The 2026 list was published on September 30, 2025, and applies to credit allocations made after December 31, 2025. A project that files a complete application while its site is on the list generally keeps that status if credits are allocated within 730 days.

States have their own lever too. Under Section 42(d)(5)(B)(v), a state housing credit agency may designate any building as needing the boost to be financially feasible. That building is then treated as if it sat in a DDA, but this option does not apply to buildings financed under the tax-exempt bond route.

DDA vs. Qualified Census Tract

Example

Suppose two identical 60-unit projects each have $15 million in eligible basis. One sits in a DDA and one does not. The DDA project calculates its credits on $19.5 million instead of $15 million, so it can earn up to 30% more credit, and raise correspondingly more investor equity, for the same building.