Welcome to the Seneca Township Assessor’s home page. From this page you will be able to search for Parcel information including sales, link to the County GIS system, link to the County Assessments webpage, send the assessor’s office a message and more as items are needed.

Seneca Township 2023 Equalization

The 2023 Seneca Township Equalization Factor is 1.1099. This was determined by the Illinois Department of Revenue in a three-year sales ratio study which analyzes the arms’ length sales that have occurred in 2020, 2021, and 2022 and compares them to the prior year’s assessment values. The sales ratio study is done by the Illinois Department of Revenue for every county and township in the State of Illinois annually. The most recent data has determined that the 2023 assessments, in Seneca Township as whole, must be increase by 1.1099 over the 2022 assessment levels.

The 2023 equalization factor of 1.1099 DOES NOT mean that house values have increased. This is a method used in order to assess the township as a whole at the statutory 33.33% of fair cash value. This allows you to check your final assessment for the year by keeping a correlation to market values since market values have increased significantly recently.


If recent sales in your subdivision and neighborhood indicate that your parcel is overvalued after the application of the 2023 equalization factor, then that is a basis for an assessment appeal. Additionally, if your property or home is over-assessed compared to other similar properties or homes in your subdivision or neighborhood, this would also be a legitimate basis for an appeal. Property owners will not be able to appeal an assessment value based solely on the 1.1099 equalization factor.

More information on the appeal process is located at: McHenry County Assessments Website

Parcel and Sales Search***

You need any combination of the items below:

  • a Property Index Number, PIN, in the following format: 12-##-###-###. (All Seneca Township PIN’s begin with 12)
  • or, any part of an address, home # or Street Name, (e.g. 16506 or Garden Valley)
  • and/or, Neighborhood (i.e. Subdivision)
  • and/or, for Sales Searches type in a date, (all sales after that date will be displayed.)
  • and/or, a Type of property (e.g.. 1.0 story, 2.0 story, split)

***The data contained on this website is public record, made available by the Freedom of Information Act and Illinois Code. Use of this site is intended for research purposes only. Any other use is strictly forbidden.

Occasionally, this data may contain errors. Information gathered from this website cannot be used as a basis for argument until it has been verified as accurate by the Assessor’s Office.*** By clicking the I Agree button below, you acknowledge that you understand and accept the above statement.


Seneca Township Sales Between 05/2022 thru 09/2023

Download Spreadsheet

McHenry County GIS

Click on the following link to see your Parcel via the McHenry County Aerial maps:

McHenry County GIS


You can use the Layers Tools to view Parcel Dimensions, Farm Land Assessments or any other helpful layers. The Basemaps can be used to see the Aerial of the PIN you are researching.


The 2013 Aerial of our Township building with the Farm Assessment and Parcel Text Layers ON is shown above.

McHenry County Assessment Link

Visit the following link for much more on Assessments in the McHenry County:

McHenry County Assessments Website


If you have any additional comments, questions, or require a field review to correct any erroneous information, please contact the office at:

Tammy Benitez
16506 Garden Valley Rd.
Woodstock, IL 60098
Phone (815) 923-5922