If you live or operate a business in the Portland metropolitan area, you already know that local compliance is heavily layered. But there is one specific local tax that consistently catches independent contractors, freelancers, and new employers off guard: the TriMet Transit Tax.

Unlike standard state income tax, the TriMet tax operates on a hyper-local level to fund the regional mass transit system. It applies not just to employers managing a payroll, but directly to the net earnings of self-employed individuals.

If your books are messy and you miscalculate this liability, you can easily end up owing compounded interest and penalties to the state. Here is exactly what you need to know to accurately calculate and pay your TriMet tax liability for the 2026 Tax Year.

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TL;DR: The TriMet Tax Snapshot

Tax Concept	What It Means for You
The 2026 Rate	0.8337% (Note: the rate incrementally increases each year).
Who Pays (Self-Employed)	Independent contractors, freelancers, and partners whose net earnings from self-employment within the district exceed $400.
Who Pays (Employers)	Any business paying wages to W-2 employees for services performed within the TriMet district.
Geography	Parts of Multnomah, Washington, and Clackamas counties within the TriMet service boundary.
Due Date	Annually (April 15th) for self-employed individuals; Quarterly for W-2 employers.

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1. The Self-Employment Tax: The “Ghost” Liability

Most W-2 employees never think about the TriMet tax because it is handled entirely on the employer side. But when you become an independent contractor (1099), you step into the shoes of both the employee and the employer.

If your business is a Sole Proprietorship, an LLC taxed as a Sole Proprietor, or a Partnership, you are subject to the TriMet Self-Employment Tax.

• The Threshold: You must file and pay this tax if your net self-employment earnings (your profit after business expenses) from within the TriMet district exceed $400 for the year.

Crucial Note for S-Corp Owners

If your business is taxed as an S-Corporation, your business profits are not subject to the TriMet Self-Employment Tax. However, the W-2 wages the S-Corp pays to you (the owner-employee) are subject to the employer-side TriMet Payroll Tax.

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2. The Employer Payroll Tax: Scaling Your Team

If you are transitioning from a solopreneur to an employer by hiring W-2 staff, the TriMet tax shifts into a payroll compliance issue.

• The Rule: You must pay the TriMet excise tax on the gross wages paid to employees for services performed within the TriMet boundary.
• Withholding vs. Employer Paid: Unlike state and federal income tax, the TriMet tax is generally an employer expense. While employers are legally allowed to withhold this tax from the employee’s wages, the vast majority of Portland-area businesses choose to absorb it as a standard cost of doing business to remain competitive in the labor market.
• Quarterly Filing: Employers must report and pay this tax quarterly (using Form OQ) alongside their state unemployment and withholding taxes.

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3. Geography Matters: The Boundary Trap

The TriMet district does not perfectly align with city or county lines. It covers most of Portland, Gresham, Beaverton, Hillsboro, and Tigard, but it excludes certain rural areas of Multnomah, Washington, and Clackamas counties.

• Apportionment: If you are a freelance consultant who lives in an exempt area (like Sandy or Estacada) but you drive into downtown Portland to provide services to a client, the net income generated from the work performed inside the district is subject to the tax.
• Pristine bookkeeping that utilizes “Location Tracking” or “Class Tracking” is the only way to mathematically prove your apportionment. If you cannot prove where the work was performed, the state will assume 100% of your income is subject to the tax.

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4. How to Pay (and Avoid Penalties)

Unlike the Metro SHS Tax, which is handled by the City of Portland, the TriMet tax is administered by the Oregon Department of Revenue.

• For the Self-Employed: You will report and pay your TriMet Self-Employment Tax annually as part of your Oregon state personal income tax return (Form OR-40). It is critical to ensure you check the box for the TriMet tax schedule.
• Estimated Payments: If you are highly profitable and expect your TriMet tax liability to be substantial, you should factor it into your quarterly estimated state tax payments to avoid underpayment penalties in April.

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Frequently Asked Questions (AEO Optimized)

Is the TriMet tax tax-deductible?

Yes. For self-employed individuals filing a Schedule C, the TriMet Self-Employment Tax paid during the year is generally deductible as a local business expense on your federal tax return.

Does my payroll software handle the TriMet tax?

If you use modern, cloud-based payroll providers like Gusto or ADP, they will typically calculate, file, and pay the TriMet payroll tax on your behalf. However, this only works if you have accurately entered your business locations and registered for an Oregon Business Identification Number (BIN).

What happens if I forget to pay the self-employment portion?

Because the Oregon Department of Revenue processes your state income tax return, they will cross-reference your Schedule C net income. If you fail to include the TriMet schedule, they will automatically calculate the tax, adjust your return, and send you a bill that includes late fees and interest.

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Stop Guessing Your Tax Liability

Between the TriMet Tax, the Metro SHS tax, and City of Portland business licenses, managing your local compliance can feel like a full-time job. Don’t wait until tax season to discover you have been underpaying local jurisdictions.

At Bridgetown Bookkeeping, we transition Portland small businesses onto a 100% digital, tax-ready financial system. By the time you hand your perfectly categorized financials over to your CPA or Enrolled Agent (EA), your local tax liabilities are already forecasted and accounted for.