Ad valorem tax Latin for 'according to value.' A tax that scales with the value of the property being taxed. Property tax in the US is the canonical ad valorem tax — the rate is applied to the assessed value, so a more valuable property owes more. Appeal (assessment appeal) A formal challenge to a county's assessed value of your property. If successful, your assessed value drops and so does every future tax bill until the next reassessment. Also called a tax protest, valuation challenge, or tax grievance depending on the state. See our appeal savings calculator .
Assessed value (AV) The dollar value your county assigns to your property for tax purposes. Almost always different from market value — most counties apply an assessment ratio (e.g., 70% of market value). The mill rate is applied to assessed value (minus exemptions) to compute your tax.
Assessment ratio The fraction of market value used as the assessed value. A 70% assessment ratio means a $500,000 market-value home is assessed at $350,000. Ratios vary by state — some are 100% (Florida), some are 30–50% (parts of the South), some are state-set with annual equalization.
Assessor The county or municipal official responsible for setting assessed values. Sometimes elected, sometimes appointed. Called 'appraisal district' in Texas, 'assessor' or 'tax commissioner' elsewhere. Your first stop for questions about your assessment.
Bond / bond measure A debt issuance approved by voters or local authorities to fund a specific project (school construction, roads, parks). Repaid via a temporary or permanent addition to the local mill rate. Often appears as a separate line item on your tax bill.
Cap (assessment cap) A statutory limit on how fast assessed value can rise year-over-year. California's Prop 13 caps at 2%, Florida's Save Our Homes at 3% or CPI, Texas at 10% on homestead, Michigan at 5% or CPI. Caps reset on sale in most states.
Certified rate / certified roll The official, finalized mill rate (or assessment roll) for a tax year, after public hearings and budget adoption. The rate before certification is preliminary and may change.
Clerical error An incorrect entry on your county property record card — wrong square footage, bedroom count, lot size, construction year, condition rating. Usually correctable without a full appeal; just a request to the assessor with documentation.
Community Development District (CDD) A special-purpose district common in Florida master-planned communities. Funds infrastructure (roads, water, parks) via a separate assessment on top of regular property tax. Adds 0.5–2.0% effective rate; appears as a separate bill or line item. Effective tax rate Annual property tax paid divided by home market value, expressed as a percentage. The most honest cross-jurisdictional comparison because it folds in assessment ratios, exemptions, and special districts. See our effective rate calculator .
Equalization / equalization factor A state-level multiplier applied to county assessed values to bring all counties to a consistent target ratio of market value. Most visible in Illinois, where the 'equalized assessed value' (EAV) is your county AV times the state factor. Escrow / impound account A mortgage servicer–held account that collects monthly contributions toward your annual property tax and homeowners insurance and pays the bills on your behalf. RESPA caps the cushion at two months. Called 'impound' in the Western US. See our escrow calculator .
Exemption A reduction in taxable value before the rate is applied. Common types: homestead (primary residence), senior (65+), veteran (especially disabled), disability, agricultural, historic preservation. Most stack on top of each other.
Headlee Amendment / Proposal A Michigan's twin caps: Headlee (1978) limits how fast a taxing unit's revenue can grow; Proposal A (1994) caps annual taxable-value growth on individual properties at 5% or CPI, whichever is lower. Resets on sale. Homestead Your primary residence — where you live, vote, and intend to remain. The qualifying property for the homestead exemption (and, in some states, separate homestead protection from creditors). See our homestead savings calculator .
Itemized deduction Listing individual deductible expenses on your federal tax return (Schedule A) instead of taking the standard deduction. Property tax (capped at $10,000 SALT) is one of the largest itemizable deductions for most homeowners.
Mello-Roos A California special-tax district authorized by the 1982 Mello-Roos Community Facilities Act. Used to fund infrastructure in newer developments. Adds a fixed annual special tax (often $1,000–$5,000+) on top of the regular Prop-13-capped property tax. Mill / millage / mill rate A mill is one one-thousandth of a dollar. A mill rate of 18.5 means $18.50 of tax per $1,000 of assessed value. Used to express property tax rates in much of the Northeast and Midwest. See our mill rate calculator .
Municipal Utility District (MUD) A Texas (and some other states') special district that funds water, sewer, and drainage in unincorporated areas — common in Houston-area master-planned communities. Adds a separate property tax line item, often 0.5–1.5%.
Notice of Valuation / TRIM Notice The annual mailer your county sends with your new assessed value (and, in Florida, the proposed mill rates and resulting tax — TRIM stands for 'Truth in Millage'). Starts the appeal-deadline clock. Read it the day it arrives.
Parcel / parcel number The unique identifier your county uses for your property. Sometimes called APN (Assessor's Parcel Number), PIN (Property Identification Number), or PID. The number you'll need on every form, every appeal, every search.
Pass-Through Entity (PTE) tax A state-level workaround to the federal SALT cap. Lets owners of S-corps and partnerships pay state taxes at the entity level (federally deductible) rather than on their personal return (capped). Available in NJ, NY, CT, MA, CA, CO, and many other states.
Personal property tax Tax on movable property (mainly vehicles) levied annually in some states (VA, MA, MO, KY, MS, RI, AR, etc.). Distinct from real-estate property tax but counted as part of SALT for federal deduction purposes.
Prop 13 California Proposition 13 (1978). Caps property tax at 1% of assessed value plus voter-approved overrides, and limits annual assessed-value growth to 2%. Resets to market on sale or new construction. The structural reason long-time California homeowners pay far less property tax than recent buyers.
Property record card The county's detailed file on your property: square footage, bedrooms, baths, year built, lot size, condition rating, sale history, photos. Free to view in most counties. Errors here are the easiest source of appeal wins. Reassessment The periodic update of a property's assessed value — annual in most of TX/FL/GA, every 2–3 years in many Northeast/Midwest states, on sale/construction triggers in CA-style states. Often the largest single driver of tax bill changes. See our reassessment impact calculator .
RESPA Real Estate Settlement Procedures Act (1974). Federal law governing how mortgage servicers handle escrow accounts. Caps the escrow cushion at two months and requires an annual escrow analysis with refunds for overages over $50. SALT (State and Local Tax) Federal-tax shorthand for state and local taxes — primarily state/local income tax (or sales tax), plus property tax. The 2017 Tax Cuts and Jobs Act capped the deduction at $10,000 per return. See our SALT cap calculator .
Save Our Homes (SOH) Florida's constitutional cap (1995) on annual assessed value growth for homestead properties — the lower of 3% or CPI. One of the most valuable benefits of Florida homestead status; partially portable to a new Florida homestead within three years.
School district An independent local government with its own elected board and taxing authority. Funds public K–12 education. School millage is typically the largest single line on a property tax bill — often 50–60% of total.
Special assessment / special district A geographically scoped tax that funds a specific local benefit (sidewalks, drainage, fire protection). Distinct from general property tax. Examples: CDDs in FL, Mello-Roos in CA, MUDs in TX, PIDs in many states.
STAR (School Tax Relief) New York State's homestead-style exemption for school taxes. Basic STAR is roughly $30,000 of assessed-value exemption with income limits; Enhanced STAR is more generous for seniors. Funded as a state credit, not a local exemption.
Tax bill The annual or semi-annual statement from your county or municipality showing the assessed value, mill rates by taxing district, exemptions claimed, and total amount due. Pay close attention to line items — that's where errors hide.
Tax foreclosure / tax sale The legal process by which a county can sell or take title to a property when property taxes are unpaid for an extended period (typically 2–5 years). Rules vary widely by state. The reason mortgage servicers escrow for taxes — they want their lien protected.
Taxable value Assessed value minus exemptions, multiplied by any equalization factor. The number to which the mill rate is actually applied. Always smaller than (or equal to) the assessed value if you have any exemptions.
Truth-in-taxation State laws (TX, FL, NV, others) requiring local taxing authorities to publicly notify and hold hearings before adopting a budget that requires raising more revenue than the prior year. Forces some transparency on rate increases.