Seattle Business Filing Deadlines & Ongoing Requirements

Annual federal income tax return (extensions available via Form 7004 / 4868).

Free, one-time federal tax ID needed for tax filings, payroll and bank accounts.

Businesses holding property that has gone unclaimed — uncashed payroll or vendor checks, customer credits and refunds, unused gift cards, deposits — must report and turn it over to the state each year, after sending the owner a due diligence notice before the deadline. The annual report and payment are due October 31 for general property. Life insurance reports are due April 30. Which state's law applies depends on the owner's last known address, or the business's state of incorporation when there is none, so a business can owe reports to several states.

Fee: $70. Required to keep the entity in good standing.

A person or service with a physical Washington address to receive legal notices and service of process; listed with Washington Secretary of State, Corporations and Charities.

Business & Occupation (B&O) tax on gross receipts; no corporate or individual income tax.

Fee: $90 (varies by endorsements). General state license required to operate in Washington.

If personal information of residents of the state is acquired without authorization, notify affected residents within 30 days of discovering the breach and the Attorney General if more than 500 residents are affected (RCW 19.255.010). This is an event-driven duty, so it has no calendar date. Sources in the PR describe the state's rule in different words; check the statute for the exact trigger and content of the notice.

Washington personal property listings are due to the county assessor by April 30 for equipment held on January 1. Listings can be filed on paper or through eListing; late listings take a 5% monthly penalty up to 25%, and no extensions are granted.

City licenses are added as endorsements to the state business license; Seattle and others levy local B&O taxes.

The commercial space must be approved for its intended use before operating.

Seattle requires a business license tax certificate (via the state Business Licensing Service) and a Seattle B&O tax return when taxable revenue exceeds the threshold.

Withheld income tax, Social Security and Medicare, plus employer share, via EFTPS.

Quarterly reconciliation of wages and payroll taxes.

Annual FUTA return and payment.

Wage statements to employees and transmittal to the SSA.

Employment eligibility verification, retained for 3 years after hire or 1 year after termination.

Employers must post the FLSA minimum wage, FMLA (50+ employees), EEO, OSHA, USERRA and related notices in a conspicuous place.

Employer account for state unemployment insurance contributions.

Quarterly wage report and contribution payment. Washington taxes the first $78,200 of each employee's wages (2026); new employers pay the industry average rate, and experience-rated rates range from 0% to 5.4%.

Federal law requires reporting each new hire within 20 days of hire (some states require sooner).

Coverage must be purchased from the exclusive state fund. Required at: 1 employee.

Employers report hours and remit premiums quarterly.

Washington requires employers with 1+ employees to provide paid sick leave, post notice and keep records.

State minimum wage, unemployment insurance, workers' compensation and anti-discrimination notices must be posted where employees can see them.

Employers with more than 10 employees keep Forms 300 and 301 for work-related injuries and illnesses, and post the Form 300A summary for the previous year at each establishment from February 1 through April 30. Records are kept five years. Report a work-related fatality within 8 hours and an inpatient hospitalization, amputation or loss of an eye within 24 hours.

Applicable large employers (50 or more full-time employees, counting part-time hours as full-time equivalents) give each full-time employee a Form 1095-C. The January 31 deadline is extended automatically by 30 days, to March 2 in most years (March 1 for the 2026 forms).

The transmittal Form 1094-C and each Form 1095-C are due to the IRS at the end of February on paper or March 31 electronically; employers filing 10 or more information returns in total must file electronically. Penalties apply per late or incorrect form.

Private employers with 100 or more employees file annually through the EEOC's online system; federal contractors with 50 or more employees and certain contracts have also filed. The EEOC sets each year's window (the 2024 report was due June 24, 2025, with no extensions), so check its data collections page.

Establishments with 250 or more employees submit their Form 300A summary through OSHA's Injury Tracking Application by March 2. Establishments with 20 to 249 employees in designated higher-hazard industries must also submit the summary, and those with 100 or more in the most hazardous industries submit Forms 300 and 301 data.

Quarterly estimated payments by owners on business income (Form 1040-ES), including self-employment tax.

Required for each non-employee paid $2,000 or more in the year (payments made after 2025).

Required before making taxable sales; register with the state tax agency.

Collect sales tax from customers and remit on the filing frequency assigned by the state. Local sales taxes are collected and remitted on the same state return; the rate depends on the delivery location.

Home-based businesses need a home occupation permit and must comply with zoning limits (signage, customers, employees).

Washington registers assumed names at the state level.

Articles of Organization (Certificate of Formation/Organization in some states).