HonestCasa logoHonestCasa
All Tax Guides
Updated 2025 Tax Year

Island County
Property Tax Guide

Everything you need to know about property taxes in Island County, WA. Rates, due dates, exemptions, and how it affects your monthly payment.

10 Official Sources
8 min read
Calculate Your True CostMortgage Calculator
Quick Facts
Tax Rate
0.935% effective rate (varies by taxing district and location within county)
1st Due
Apr 30
2nd Due
Oct 31
Exemptions
5+ Available
Section 1

How Property Tax Works

Island County, Washington operates under the state's property tax system, which serves as the primary funding source for essential local services including schools, fire protection, libraries, and county operations. Property taxes in Island County are calculated using assessed values determined by the County Assessor and tax rates set by various local taxing districts. The effective tax rate for Island County properties is approximately 0.935% based on 2024 data, though this can vary significantly depending on your specific location within the county.

Actual tax rates differ throughout Island County due to special taxing districts such as school districts, fire districts, hospital districts, and other local improvement areas. Properties in Coupeville may have different rates than those in Oak Harbor or unincorporated areas due to these overlapping jurisdictions. The county uses a split payment system with taxes due twice annually, and most tax credits and exemptions require separate applications and are not automatically applied to your property tax bill.

Section 2

What Makes Up Your Tax Bill

ComponentRate RangeDescription
County General~2.50-3.00 per $1,000Basic county services, courts, sheriff
School Districts~4.00-8.00 per $1,000Varies by district (Oak Harbor, Coupeville, South Whidbey)
Fire Districts~1.00-2.00 per $1,000Emergency services, varies by district
Hospital District~0.50-1.00 per $1,000WhidbeyHealth Public Hospital District
Library District~0.30-0.50 per $1,000Sno-Isle Libraries
Port Districts~0.20-0.50 per $1,000Port of Coupeville, Port of South Whidbey
Total Combined~6.43-9.43 per $1,000Actual rate varies by location

Rates shown are for levy year 2024-2025 and vary significantly based on specific taxing districts serving your property location. Contact Island County Assessor for your exact rate.

Section 3

When Are Property Taxes Due?

For the 2025/2026 tax year in Island County, property taxes are due in two installments:

First Installment
Apr 30
Delinquent after Dec 10
Second Installment
Oct 31
Delinquent after Apr 10
Pro tip: If you pay through mortgage escrow, your lender splits these payments across your monthly mortgage. If you pay directly, set calendar reminders to avoid late penalties.
Section 4

Supplemental Tax Bills

Supplemental taxes in Island County are additional property tax bills issued when there are mid-year changes to property ownership, new construction completion, or significant improvements that increase assessed value. These taxes cover the difference between what was already billed and what should have been billed based on the property's current status. Common triggers include completing new home construction, finishing major renovations like additions, or purchasing newly constructed property.

Supplemental taxes are calculated by taking the difference between the old and new assessed values, multiplying by the applicable tax rate, and prorating for the portion of the tax year remaining. For example, if you complete a $100,000 home addition in January and your total tax rate is 9.43 per $1,000, you would owe approximately $943 in supplemental taxes for the remainder of that tax year. These bills are typically issued within 30-60 days of the assessor receiving notification of the change.

Example Calculation

Property Value: $300,000

  • Assessed Value: $300,000
  • Less: Senior/Disabled Exemption (if qualified): -$60,000
  • Net Taxable Value: $240,000
  • Tax Rate: 9.43 per $1,000 = $2,263
  • Monthly Escrow: $189

Property Value: $600,000

  • Assessed Value: $600,000
  • Less: Senior/Disabled Exemption (if qualified): -$60,000
  • Net Taxable Value: $540,000
  • Tax Rate: 9.43 per $1,000 = $5,092
  • Monthly Escrow: $424

Property Value: $1,000,000

  • Assessed Value: $1,000,000
  • Less: Senior/Disabled Exemption (if qualified): -$60,000
  • Net Taxable Value: $940,000
  • Tax Rate: 9.43 per $1,000 = $8,864
  • Monthly Escrow: $739

Note: Senior/Disabled exemptions require annual application and income qualification. Tax credits are not automatically applied.

See How Taxes Affect Your Payment

Property taxes are just part of your total monthly cost. Get the full picture.

Calculate Now
Section 5

Escrow & Property Taxes

Most mortgage lenders in Island County require borrowers to maintain an escrow account for property taxes, collecting monthly payments alongside principal and interest. Lenders typically collect 1/12th of your annual property tax bill each month, holding these funds in a separate account to pay your taxes when due. Your lender will pay the first half by April 30th and second half by October 31st directly to Island County Treasurer.

Annual escrow analysis statements from your lender show whether you have a shortage or surplus based on actual tax bills versus collected amounts. If Island County increases tax rates or your assessed value rises significantly, you may face an escrow shortage requiring increased monthly payments or a lump sum payment. Property owners should verify that lenders pay taxes on time, as you remain ultimately responsible for timely payment even when using escrow services. You can verify payments on the Island County Treasurer's website using your parcel number.

How HonestCasa Helps
  • Understand whether your escrow is set correctly
  • See how rising taxes will change your monthly payment
  • Plan ahead instead of being surprised by "shortage" letters
Section 6

Frequently Asked Questions

Q: When are property taxes due in Island County for 2024-2025? A: First half taxes are due April 30, 2025, and second half taxes are due October 31, 2025. Payment forms must be delivered by March 15th and September 15th respectively for each half.

Q: What tax credits are available and do they require application? A: The primary tax credit is the Senior/Disabled exemption which can exempt up to $60,000 in assessed value. This requires annual application with income documentation. Most tax relief programs require separate applications and are NOT automatically applied.

Q: How does the Senior/Disabled property tax exemption work? A: This is an exemption that reduces your taxable assessed value by up to $60,000 if you meet age (61+), disability, or income requirements. You must apply annually with Island County Assessor, and income limits apply based on household size.

Q: When does Island County reassess properties? A: Washington law requires annual revaluation with physical inspections on a 6-year cycle. Island County typically updates assessed values each January 1st for the following year's taxes. Assessment notices are mailed in late spring.

Q: How do I appeal my property assessment? A: File an appeal with Island County Board of Equalization by July 1st following assessment notice. You can present evidence of comparable sales, property condition issues, or errors in assessment data.

Q: What are the penalties for late property tax payments? A: Interest begins accruing June 1st on first half payments and December 1st on second half payments. After three years of delinquency, properties may be subject to foreclosure proceedings.

Q: Can I pay property taxes online? A: Yes, Island County Treasurer accepts online payments through their website using bank transfer or credit/debit cards. Processing fees may apply for credit card payments.

Q: Why do tax rates vary within Island County? A: Different areas are served by different combinations of school districts, fire districts, library districts, and other special taxing districts. Oak Harbor, Coupeville, and rural areas have different service providers resulting in different total tax rates.

Verified Sources

Backed by 10 Official Government Sources

Every fact in this guide is sourced from official county, state, and federal documents.

01
Property Details - 14 DFF for Year 2025 - 2026assessor.islandcountywa.gov
02
Tax Doc
PROPERTY TAX STATISTICS 2025dor.wa.gov
03
2025 Proposed Budgetislandcountywa.gov
04
County
Treasurer | Island County, WAislandcountywa.gov
05
County
Personal Property Taxes | Island County, WAislandcountywa.gov
06
County
Paying Property Taxes | Island County, WAislandcountywa.gov
07
County
Exemptions | Island County, WAislandcountywa.gov
08
County
Frequently Asked Questions - Island County, WAislandcountywa.gov
09
Tax Doc
Property Tax Exemptions and Deferrals Manualpropertytax.dor.wa.gov
10
County
Real Estate Excise Tax | Island County, WAislandcountywa.gov
All sources verified as of 2025 Tax Year

See the Full Picture of Your Home Costs

Property taxes are just one piece of homeownership. HonestCasa helps you understand your total monthly cost and explore safe ways to access your home equity.

Total Monthly Cost

Mortgage + taxes + insurance + HOA

Equity Growth

Track how your equity grows over time

Safe Equity Access

Options for projects or debt payoff

Run Your ScenarioTry Calculator

Free • No credit check • 2-minute estimate