Most S-corp owners can tell you their revenue, their payroll, and their profit. Ask them their basis, and the room goes quiet. That is a problem — because basis quietly controls three of the most important tax moments you have: whether you can deduct a loss, whether your distributions are tax-free, and what you owe when you sell. Here is how it works, in plain English, and the mistakes we see most.

What “Basis” Actually Means

Basis is your investment in the company, measured for tax purposes. Think of it as a scorecard the IRS keeps for your share of the business.

It starts with the money or property you put in. It goes up when the company makes money. It goes down when you take money out, or when the company loses money. That running number is your basis.

Basis is not your bank balance. It is not your profit. It is not what the business is “worth.” It is a separate tax figure that follows you every year you own the company — and most owners never see it.

The Two Kinds of Basis in an S-Corp

In an S-corp, you actually have two separate basis numbers. Keep them apart — mixing them up is one of the most common errors we end up fixing.

Stock basis

This is your basis from owning the company. It starts with what you paid for your shares, or the cash and property you put in to start it. It grows when the company earns money, and it shrinks when you take distributions or the company has a loss.

Debt basis

This is your basis from lending money to the company — directly, out of your own pocket. If you personally loan the business $50,000, you now have $50,000 of debt basis.

Here is the part that trips people up: only a real, direct loan from you counts.

How Your Basis Goes Up and Down

Basis is a running total, and it moves in a set order each year: income first, then money out, then losses. Here is the short version.

Two rules matter most. First, your basis can never go below zero. Second, losses come off after distributions. So a distribution can use up the very basis you needed to deduct a loss.

That ordering is small print most owners never see — and it is exactly where a good year of distributions can quietly cancel out the tax benefit of a bad year of losses.

The Three Places Basis Shows Up

Basis is not a number for its own sake. It decides real dollars in three moments.

1. When you want to deduct a loss

You can only deduct your share of the company’s losses up to your basis — stock basis plus debt basis. If the loss is bigger than your basis, the extra is not gone, but it is frozen. You carry it forward until you have basis again. Many owners deduct the full loss anyway, not realizing they were not allowed to. That is one of the IRS’s favorite things to check.

2. When you take a distribution

Distributions from an S-corp are usually tax-free — but only up to your stock basis. Take out more than your basis, and the extra is taxed as a capital gain. Owners are often shocked by this. They moved “their own money” out of “their own company” and got a tax bill. The issue was never the distribution. It was that basis ran out.

3. When you sell the business

Your gain on a sale is the price minus your basis. If basis was tracked correctly over the years, you pay tax on the right number. If it was not, you either overpay — or you under-report and hear from the IRS later. By the time you sell, rebuilding years of missing records is hard and expensive.

The Basis Mistakes We Keep Seeing

This is where most of the damage happens. It is the same short list, year after year.

No one is tracking it

This is the big one. Basis has to be carried forward and updated every single year. Many owners — and, honestly, some preparers — never keep a basis schedule. Then a loss year or a sale arrives, and there is nothing to support the number.

Deducting losses you don’t have basis for

A Schedule K-1 (your yearly statement of income and loss from the company) shows a loss, so it goes on the return. But if there was not enough basis, that deduction was not allowed. The IRS has named this a focus area.

Distributions bigger than your basis

The surprise capital gains tax described above — on money the owner assumed was tax-free.

Confusing the two basis types — or the guarantee myth

Treating a loan guarantee as basis, or mixing stock basis and debt basis together, produces numbers that do not hold up under review.

Skipping Form 7203

This one now has the IRS’s attention directly. More on it next.

Form 7203 and the IRS

For the last several years, the IRS has required many S-corp owners to file Form 7203 with their personal return. In plain terms, it is your basis worksheet, made official.

You generally must attach it for any year in which you:

• deducted a loss from the company,
• took a distribution from the company,
• received a loan repayment from the company, or
• sold or disposed of your shares.

The IRS also recommends preparing it every year — even when you do not have to file it — so your basis stays current and ready.

A Timely Example: Write-Offs You Can’t Always Use

Here is where this gets very current. Under the tax law signed in 2025, businesses can again write off 100% of many equipment and asset purchases right away — full bonus depreciation is back for qualifying property bought after January 19, 2025.

That sounds like pure upside, and often it is. But a large, fast write-off can create a big paper loss on your K-1. And you already know the catch: you can only deduct that loss up to your basis.

So an owner buys equipment, expects a large deduction, and then learns that part of it is frozen — because basis ran out. The deduction is not lost forever. But it does not help this year, which is usually the exact year they were counting on it.

This is the kind of thing a short basis conversation before year-end can catch. The write-off is real. Whether you can use it this year depends on a number most owners never check.

Partnerships: The Short Version

If you own part of a partnership or a multi-member LLC, basis matters just as much — with one important difference.

Partnerships deal with two views of basis. Outside basis is your basis in your share of the partnership. Inside basis is the partnership’s basis in its own assets. For most owners, outside basis is the one that drives your tax outcome, and it works a lot like S-corp basis: it limits your losses, and a distribution larger than your basis creates a taxable gain.

The big difference is debt. In a partnership, your share of the company’s debt usually adds to your basis — even debt from a bank. That is the opposite of an S-corp, where only a direct loan from you counts.

Because partnership basis includes debt, it can shift every year as loans rise and fall. That makes year-to-year tracking just as important here — and there is no Form 7203 reminding you to do it.

What Good Basis Tracking Looks Like

Basis problems are almost always preventable. They come from neglect, not bad luck. Staying ahead of it looks like this.

• A basis schedule for each owner, updated every year — not reconstructed under pressure at filing time.
• Stock basis and debt basis tracked separately, with clean records of any loans you have personally made to the company.
• Form 7203 prepared annually, whether or not it has to be filed that year.
• A basis check before you take a large distribution, claim a big loss, or buy major equipment — while you can still adjust.
• A basis figure that is ready and defensible the day you decide to sell.

Frequently Asked Questions