24 C.F.R. § 886.312

(a) Limits. Housing assistance payments will be made in amounts commensurate with contract rent adjustments under this paragraph, up to the maximum amount authorized under the contract. (See § 886.308.)

(b) Annual adjustments. The contract rents may be adjusted annually, at HUD's option, either (1) on the basis of a written request for a rent increase submitted by the owner and properly supported by substantiating evidence, or (2) by applying, on each anniversary date of the contract, the applicable automatic annual adjustment factor most recently published by HUD in the Federal Register. If HUD requires that the owner submit a written request, HUD within a reasonable time shall approve a rental schedule that is necessary to compensate for any increase occurring since the last approved rental schedule in taxes (other than income taxes) and operating and maintenance costs over which owners have no effective control, or shall deny the increase stating the reasons therefor. Increases in taxes and maintenance and operating costs shall be measured against levels of such expenses in comparable assisted and unassisted housing in the area to ensure that adjustments in the contract rents shall not result in material differences between the rents charged for assisted and comparable unassisted units. Contract rents may be adjusted upward or downward as may be appropriate; however, in no case shall the adjusted rents be less than the contract rents on the effective date of the contract, provided there was no fraud or mistake adverse to the Department's interest in determining the initial contract rent.

(c) Special adjustments. Special adjustments in the contract rents shall be requested in writing by the owner and may be authorized by HUD to the extent HUD determines such adjustments are necessary to reflect increases in the actual and necessary expenses of owning and maintaining the contract units which have resulted from substantial general increases in real property taxes, utility rates or similar costs (i.e., assessments and utilities not covered be regulated rates) which are not adequately compensated for by the adjustment authorized by paragraph (b) of this section.

(d) Comparability between assisted and unassisted units. Notwithstanding any other provisions of this subpart, adjustments as provided in this section shall not result in material differences between the rents charged for assisted and comparable unassisted units, as determined by HUD: Provided, however, That this limitation shall not be construed to prohibit differences in rents between assisted and comparable unassisted units to the extent that such differences may have existed with respect to the initial contract rents assuming no fraud or mistake adverse to the Department's interest.

(e) Addendums to contract and leases. Any adjustment in contract rents shall be incorporated into the contract and leases by dated addendums to the contract and leases establishing the effective date of the adjustment.