Documentation

Method

This page explains how Debugging Fairfax calculates the estimated impact of Fairfax County budget changes on an individual property tax bill.

Overview

Debugging Fairfax shows how Fairfax County tax dollars are allocated and how those allocations are changing between fiscal years. The goal is to make the county budget easier to understand for residents by translating large budget numbers into real-world impacts on an individual property tax bill.

Data Sources

The analysis is based on publicly available Fairfax County budget documents, including adopted fiscal year budget reports and departmental appropriation tables.

  • Fairfax County Adopted Budget FY2026
  • Fairfax County Proposed Budget FY2027
  • Departmental appropriation summaries

How the Calculation Works

The calculator estimates tax bill changes using only home assessment and tax rate adjustments entered by the user.

  1. The user enters a current annual real estate tax bill.
  2. The user can adjust the assumed home assessment change.
  3. Tax rate change defaults to 0% unless changed.
  4. Estimated tax bill change is calculated as: (assessment change + tax rate change) x current tax bill.

What the Calculator Shows

The calculator highlights which spending categories are driving the largest changes in your property tax bill between fiscal years.

  • Total estimated change to your tax bill
  • Percentage increase or decrease
  • The budget categories responsible for the largest changes

Important Notes

  • This tool estimates bill changes from assessment and tax rate inputs. County spending does not directly change the calculation.
  • Budget category sections are provided for transparency context, not as direct drivers in the tax bill math.

Transparency

Debugging Fairfax is an independent civic data project. All calculations are based on publicly available Fairfax County budget documents.

  • All source data comes from official county budget reports.
  • The calculation logic is documented on this page.
  • The code used to generate the analysis is publicly available.
View the code on GitHub →

Debugging Fairfax is an independent civic data project focused on making local government finances easier to understand.

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