When is the deadline to file small business taxes in Washington?

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Small businesses in Washington must adhere to a combination of federal, state, and local filing deadlines. At the federal level, calendar-year taxpayers generally file Form 1120 for corporations or Schedule C on Form 1040 for sole proprietors by April 15. Washington state imposes Business & Occupation (B&O) tax returns quarterly or annually, depending on gross revenue thresholds, with the primary annual B&O return due April 30. Cities like Seattle may require additional annual business license renewals by the last day of the business’s anniversary month. Understanding these layered deadlines is essential to maintain compliance and avoid penalties.

Federal Tax Deadlines for Small Entities

For federal filings, small C corporations (Form 1120) follow a deadline of April 15 for calendar-year filers, unless that date falls on a weekend or holiday, in which case the deadline shifts to the next business day. Partnerships (Form 1065) and S corporations (Form 1120-S) file by March 15. Sole proprietors report business income on Schedule C of individual returns, also due April 15. Estimated tax payments—Form 1040-ES for individuals or Form tax services near me seattle wa 1120-W for corporations—are due quarterly: April 15, June 15, September 15 and January 15 of the following year. Missing these dates risks failure-to-pay penalties and accruing interest on unpaid balances.

Washington State B&O and Sales Tax Filings

Washington’s B&O tax applies to gross receipts rather than net income. Businesses with annual gross revenue over $100,000 must file B&O returns quarterly, due April 30, July 31, October 31 and January 31. Those below the threshold may elect annual filing by April 30. Retailers also file sales tax returns on the same quarterly schedule unless their volume requires monthly filings. Late submissions incur a penalty of 5% of the tax due, plus interest. Accurate bookkeeping and timely reconciliations ensure that gross receipts are reported correctly, avoiding underreporting risks.

Local Business License Renewal Dates

Seattle requires all businesses operating within city limits to renew their business license annually. The renewal deadline is the last day of the business’s initial license month—commonly December 31 for calendar-year applicants. Renewal involves submitting gross receipts, UBI numbers and license fees via the City of seattle wa cpa firms Seattle’s business license portal. Failure to renew can result in license suspension and fines. Aligning city renewal with state and federal filings simplifies the compliance calendar.

Extensions and Amended Returns

Businesses may request automatic extensions to file federal returns: six months for C corporations (moving from April 15 to October 15) and five months for S corporations and partnerships (extending to August 15). Washington does not grant B&O extensions beyond April 30, though payment plans may be arranged. State allows amended B&O returns within four years of the original due date. Filing an extension requires submitting Form 7004 at the federal level before the original deadline, but extension of time to file is not an extension to pay: estimated taxes remain due on the original dates.

Penalties for Late Filings and Nonpayment

Federal late-filing penalties are 5% of unpaid tax per month, capped at 25%, plus interest. Washington’s late B&O filing penalty is 5% per month of the tax due, capped at 25%, with 12% annual interest. Seattle business license late renewals incur a $50 penalty plus 12% interest on outstanding fees. Combined penalties across jurisdictions can accumulate rapidly, underscoring the importance of an integrated calendar that tracks each Service Type and associated Financial Document deadline.

How George Dimov CPA Helps You Stay Ahead

George Dimov CPA offers a consolidated compliance calendar that maps federal, state and local deadlines into a single workflow, ensuring that each Service Type—from Form 1120 filings to B&O returns and city renewals—is tracked and managed proactively. We automate reminders through secure client portals, reconcile revenue data in QuickBooks Online, and prepare estimated payment worksheets for each quarter. Our team assists with extension filings, negotiates penalty abatements when justified, and delivers a clear timeline for every upcoming due date. By centralizing all deadlines and leveraging entity–relationship principles, we minimize compliance risk and free you to focus on running your business.