LLC vs S corp: what actually changes, and what to ask before you elect

An LLC is the wrapper; S corporation is the tax treatment

The IRS describes an LLC as an entity created by state statute. How it is taxed depends on how many members it has and what elections it makes. A single-member LLC is disregarded for income tax purposes unless it elects otherwise, so its profit goes on the owner's Schedule C. A multi-member LLC is treated as a partnership by default.

Massachusetts follows the federal answer. The Department of Revenue says LLCs are classified for Massachusetts income tax purposes the same way they are for federal purposes, and that entities which are S corporations federally are S corporations in Massachusetts too, apart from security corporations.

So the real question is rarely "should I form an LLC or an S corp?" It is "should my LLC, which already exists, keep its default tax treatment or elect S status?" The legal entity, its liability position and its standing with the Secretary of the Commonwealth do not change because of a tax election.

How the election is made

An LLC becomes an S corporation for tax purposes by filing Form 2553. The IRS instructions say an entity eligible to be treated as a corporation that meets the S corporation tests is treated as a corporation from the effective date of the election and does not need to file Form 8832 separately.

Timing matters. The election must be filed no more than 2 months and 15 days after the beginning of the tax year it is to take effect, or at any time during the preceding tax year. For a calendar-year business wanting S status from 1 January 2027, that means by 15 March 2027.

The IRS generally sends a determination within 60 days of filing. If you have not heard within 2 months, the instructions say to follow up. Missed the window? Relief may be available; see the page on late election relief.

Side by side: the same LLC, before and after an S election

What the election can change for the better

The case for an S election rests on one line: employment tax. As a default LLC owner, all of your net earnings are subject to self-employment tax, up to the Social Security wage base for the 12.4% part and without limit for the 2.9% Medicare part. As an S corporation owner who works in the business, you pay FICA on a reasonable salary, and the profit left after that salary passes through to you without employment tax.

There are other effects that can help some owners. Only S corporations and partnerships can elect the Massachusetts pass-through entity excise under Chapter 63D, which can matter to owners whose state taxes exceed the federal SALT cap. From tax year 2026 there is also a new Chapter 63E excise for income above the 4% surtax threshold. Neither is available to a disregarded single-member LLC.

What it costs and complicates

The same election adds work and cost. Payroll has to run for the owner, with federal and Massachusetts employment filings through the year and a W-2 at year end. The business files its own federal and state returns. Massachusetts charges the $456 minimum excise whether or not the company made money. PFML contributions apply to the owner's wages, and the 2027 PFML rate had not been set when this page was checked.

The salary also shrinks the federal QBI deduction, because wages are not qualified business income. An honest comparison nets all of this against the employment tax saved; a comparison that shows only the payroll tax line overstates the benefit.

• Payroll provider cost and the time to review each run
• The $456 Massachusetts minimum excise, every year
• PFML on the owner's W-2 wages (0.88% in 2026, 0.46% sent by employers with fewer than 25 covered individuals)
• Unemployment insurance, if DUA treats your wages as covered: a new employer's 2026 rate is 2.42% on the first $15,000
• Federal unemployment tax on the first $7,000 of wages (2026 wage base)
• A second set of returns: Form 1120-S and Form 355S
• A smaller federal QBI deduction

Questions to answer before you elect

These are the questions worth bringing to a meeting with whoever prepares your returns. None of them has a universal answer, which is why they are questions and not a checklist to tick.

• What has the business actually earned, after expenses, in each of the last two years, and what do reconciled books say about this year?
• How steady is that profit? Would a slow year leave too little to cover a salary, payroll costs and the minimum excise?
• What would it cost to hire someone to do the work you do? That is the starting point for a reasonable salary, not a percentage.
• Does anyone else in your household earn W-2 wages, and how close are you to the Social Security wage base?
• Are you ready to run payroll for yourself, including quarterly filings, and who will do each payroll task?
• How do you pay for health insurance and retirement savings now, and how would the S corporation rules change that?
• Do your state and local taxes exceed the federal SALT cap, so that the 63D or 63E pass-through excise is worth discussing?
• Is the business likely to have losses, take on debt, or add an owner, all of which interact with S corporation basis and eligibility rules?
• When would the election take effect, and can the 2 months and 15 days window still be met?
• If it turns out not to suit you, what does undoing it involve? Once made, an election stays in effect until terminated or revoked, and a new election generally needs IRS consent before the fifth tax year after that.

Where we come in

We can run the comparison with your actual numbers: your books, your household income and the Massachusetts costs listed above, shown line by line so you can see where the result comes from. If the election makes sense, we can go through what changes afterward; if it does not, you will know why. We give you a scope and a price in writing before anything starts.

Choosing and forming a legal entity is a legal question as well as a tax one. For liability or operating-agreement questions, speak to a Massachusetts attorney.