Because the Department of Assessments and Taxation has the best available data concerning property ownership, the Department has agreed to assist local governments to identify properties which are served by public water and sewer or which have septic systems. Initial identification of sewer, water, and septic was done in conjunction with the Maryland Department of Planning.

On the Site & Flags tab in AAVS (WinRDE) in the Property Characteristics section, Category 04 (Sewer System) is used to indicate the type of sewer service: 00 = Public, 01 = Septic, 02 = Cesspool, 03 = Sand Mound, 04 = None. Category 05 (Water System) is used to indicate the type of water service: 00 = Public, 01 = Private Well, 02 = Shared Well, 03 = Cistern, 04 = None. These fields are on the July billing tapes at position 463 for one character for water and position 464 for one character for sewer. It is not the responsibility of assessment office personnel to update these fields. Changes to these fields will be transmitted to the assessment office by local governments.

For septic system users, there is a charge per unit. Local governments are using the number of dwelling units to determine the number of units. This is in position 1593 for four characters. Counties may not request a change to the number of dwelling units in the residential file. However, they may send a list of properties with a number of associated units for commercial properties. These are entered or changed in the Account Flags section of the Site & Flags tab in AAVS. Flag Category “ITUT” is used for Total Units. If there is already a number of units in that field that corresponds to the number of apartments, slips, pad sites, etc. for that particular account, the county may not request a change to that field. However, if the county has determined the number of offices, retail spaces, etc. the commercial assessor may choose to enter this data into AAVS.

In the future, the Department of the Environment hopes to develop a Statewide property database to assist in the distribution of money for failing septic systems. Their database will be constructed from assessment records.​