How is K-1 income taxed? What physicians need to know about pass-through income

Every year at Gelt, we have some version of the same conversation. A physician calls because a K-1 has finally shown up, either for a practice they own a piece of or an investment they made, and they are staring at a form full of boxes asking the same thing: Do I owe tax on all of these numbers?

Usually the answer is no, but knowing why matters more than most physicians realize. A K-1 reports your share of income from a pass-through entity, an S corporation or a partnership that pays no income tax itself and instead passes its profit through to the owners to report personally. Physicians see them from two directions: owning a stake in a practice or medical group, or investing passively in something like a surgery center or a real estate deal. Read the form correctly, and you avoid overpaying, leaving a deduction behind, or getting caught off guard at filing. Here is what every physician should know about a K-1 before it hits their return.

The most common misread: profit, not the cash you took out

Here is the misconception I correct the most. Physicians assume the tax they owe equals the money they pulled out of the business. It feels logical, but with a pass-through entity, it is not how the math works. You pay tax on your share of the profit, whether or not you actually took the cash. If your practice had a strong year but reinvested most of it in new imaging equipment, a buildout or additional staff, that profit is still taxable to you even though it never hit your personal account.

The flip side surprises people just as much. Distributions are generally tax-free, because they are distributions of profit you were already taxed on, in the current year or a prior one. So, you can end up with a K-1 that reports a loss even though you received cash, or reports profit on money you never touched.

The practical takeaway is to look at the practice's profit and loss statement and your share of the profit when you plan, not your distributions. The cash that lands in your account is not the number the IRS is looking at.

Your entity type shapes what you actually owe

Not all K-1 income is taxed the same way, and the entity behind the form matters more than most physicians realize.

Many practice owners are set up as an S corporation. If that is you, your K-1 income is not subject to self-employment tax, and your compensation comes through a W-2 instead. Partnerships work differently. If you are a partner in a medical group, your share of the income may or may not be subject to self-employment tax, which runs 15.3% for Social Security and Medicare. General partners, partners who materially participate, and anyone receiving a guaranteed payment are the ones who tend to owe it.

This is worth watching, because a mistake at the partnership level flows straight onto your personal return. If you are characterized as a passive partner when you actually materially participate, or the reverse, flag it right away. Fixing it after the fact is far more painful than catching it early.

There is also the net investment income tax. If your K-1 carries interest, dividends or capital gains, that income can be subject to an additional tax, and it usually shows up in the informational boxes that are easy to skim past.

The fine print that changes your bill: footnotes and state forms

The numbered boxes get all the attention. The footnotes and statements behind them are where a lot of the real detail lives, and they are the piece I would least want a physician to ignore.

Those footnotes can tell you whether you qualify for the qualified business income (QBI) deduction, how your income is characterized and whether tax was withheld on your behalf in another state. For physicians, one detail matters more than most. A medical practice is generally a specified service trade or business, which affects whether the QBI deduction is available at your income level. Miss it, and you can end up taxing income at the wrong rate.

State K-1s deserve the same care, especially if you are part of a multi-state group or have telehealth income. When a practice operates across state lines, income gets apportioned, and state treatment does not always match federal. Those forms also carry credits you do not want to leave behind, like the pass-through entity tax you elected to pay or withholding a state collected for you as a non-resident. If you expected a state K-1 and only received the federal one, follow up before you file.

When your K-1 is late, resist the urge to file without it

K-1s are notorious for arriving late, and physicians on extension feel it every year. My advice is simple. Do not file until you have it.

This is exactly what extensions are for. Extended pass-through deadlines fall on September 15, a month ahead of the individual deadline on October 15, by design, so the information has time to reach you. If you need a number sooner, request an estimated K-1. Physicians in medical group partnerships, venture deals and angel investments get these routinely, and an estimate lets you calculate and pay what you owe on time.

What I would steer you away from is filing with an estimate and planning to amend later. Unless there is a real reason, like a mortgage application or a refund you are counting on, it tends to backfire. An amended return creates extra compliance and can take around 16 weeks to process a refund, where the original might have taken a fraction of that. Impatience is not a good enough reason to double your paperwork.

None of this means you need to decode every box yourself. That is your CPA's job. What matters is that you understand the big picture: what is actually taxable, what is not, and how your entity shapes the bill. The more you know walking into filing season, the fewer surprises will be waiting in those boxes.

Spencer Carroll is a CPA at Gelt.