LLC or S corp for a plumber in Washington (2026)

A plumber in Washington with $70,000 of profit pays $18,624 a year in tax and fees as a sole proprietor and $20,983 as an LLC taxed as an S corp, with a $49,000 salary. The S corp starts to pay at about $332,500 of profit.

+$2,359 a year

more for an LLC taxed as an S corp than a sole proprietorship in Washington, at these numbers.

Switching from a sole proprietorship to an LLC taxed as an S corp starts to pay at about $332,500 of profit, with the same settings. Setting up costs $200 once in state filing fees.

Washington, 2026: $70,000 profit, single filer

Item	Sole prop	LLC as S corp	Change
Washington business and occupation (B&O) tax, service and other activitiesdor.wa.gov, checked Oct 23, 2026	$5,565	$5,565	$0
Self-employment taxirs.gov, 2026 rates	$9,104	$0	−$9,104
Federal income taxirs.gov, 2026 rates	$3,955	$4,565	+$610
Annual Reportsos.wa.gov, checked Oct 23, 2026	$0	$70	+$70
Payroll tax on your salaryirs.gov, 2026 rates	$0	$8,303	+$8,303
State disability and paid leaveesd.wa.gov, checked Oct 23, 2026	$0	$680	+$680
Payroll service and tax return (estimate)	$0	$1,800	+$1,800
Yearly cost	$18,624	$20,983	+$2,359

What these figures count

State income tax, and state taxes on the business itself: franchise, LLC, S corp, gross receipts and excise taxes.
Social Security and Medicare on both sides of an owner salary, federal unemployment tax and the state's new-employer rate.
The 20% qualified business income deduction with its income limits and the professional-service rule.
Yearly report fees, and a cost you can change for payroll and the business tax return.

Many S corp calculators leave out state taxes and the QBI deduction, which can make the election look better than it is.

At three profit levels

Profit	Salary used	Sole prop	LLC	LLC as S corp	C corp
$50,000	$35,000	$12,791	$12,844	$14,859	$15,689
$70,000	$49,000	$18,624	$18,678	$20,983	$22,168
$100,000	$64,000	$27,891	$27,939	$30,353	$33,592

Salary is the BLS median for the job ($63,800), capped at 70% of profit. Revenue 5.3 times profit. Single filer.

What matters for plumbers

This work is not a specified service trade or business, so the 20% QBI deduction stays available above the income limit, subject to the wage limit. Plumbing is not a listed field in Treas. Reg. 1.199A-5(b)(2). law.cornell.edu
Materials pass through the business, so revenue runs well above profit. Contractor licenses are often issued to the entity, and it may need its own license and bond.

What the switch takes in Washington

File the Certificate of Formation with the state: $200 (fee).
Get an EIN from the IRS (free, online) and open a business bank account in the new name.
Check the business can elect: no more than 100 shareholders, all of them US citizens or residents (no nonresident alien owners), and one class of stock. IRS
File IRS Form 2553 to elect S corp tax treatment, within 2 months and 15 days of the start of the tax year it should apply to. See how the S corp election works.
Register with Washington as an employer and run payroll for your own salary: federal Forms 941 each quarter, Form 940 and a W-2 each year. New employers pay Washington unemployment tax at 1.53% on the first $78,200 of wages. esd.wa.gov See what payroll costs.
Federal return each year: Form 1120-S, due March 15, plus your own Form 1040.
State upkeep each year: Annual Report, $70 a year, due Last day of the anniversary month of formation.

Questions

Should a plumber in Washington form an S corp?

At $70,000 of profit, not on these figures: the S corp costs $2,359 a year more than staying a sole proprietor.

Is an LLC worth it for a plumber in Washington?

For tax, a single-member LLC changes nothing: $18,678 a year against $18,624, the difference being Washington's LLC fees. It separates business liability and is the base for an S corp election.

Other professions in Washington

Other states