When a Form 1120-S comes across a CPA's desk, the work does not begin with entering numbers into software. It begins with a set of questions about the corporation itself, such as how the owner is compensated, what changed during the year, how income is classified, whether the accumulated adjustments account has been maintained correctly, and whether every K-1 can be traced back to the Schedule K that produced it. The return is the last step. The analysis that determines whether the return is correct happens before any numbers are entered.
Most shareholders never see this process. They assume the corporate return is being handled correctly and focus on their K-1 when it arrives. Understanding what a qualified CPA actually reviews on a Form 1120-S is useful not just for context, but because it tells you exactly what gets missed when the return is treated as a data entry task rather than a tax analysis one.
Before a single schedule is touched, a CPA reviews how the corporation compensated its owner-employees during the year. According to the IRS, this is the most scrutinized aspect of every S-corp return, and for good reason. The entire tax efficiency of the S-corp structure depends on the balance between salary and distributions. A salary set too low to minimize payroll taxes is the issue the IRS pursues most aggressively on 1120-S returns.
A CPA verifying reasonable compensation is looking for:
A salary supported by Bureau of Labor Statistics data, industry surveys, and a written memo is a defensible position. A round number with no supporting documentation is a guess the IRS is entitled to challenge, and it usually does.
Tip: If your S-corp has never had a formal reasonable compensation analysis prepared, that is worth addressing before the next return is filed. The IRS has been winning these cases consistently since Watson v. Commissioner in 2012, and the documentation that defends the salary is inexpensive to produce compared to the cost of an IRS reclassification.
Once the compensation picture is clear, a CPA examines how every category of income the corporation earned during the year has been classified. Ordinary business income, rental income, capital gains, interest, dividends, and guaranteed payments each flow to different lines of Schedule K because each is taxed differently on the shareholder's personal return. Placing any item on the wrong line changes the tax treatment for every shareholder who receives a K-1 from that Schedule K.
The income items most commonly misclassified include:
Each of these misclassifications produces a K-1 that sends the wrong information to the shareholder's personal return, and the shareholder's personal preparer typically does not catch it unless they cross-reference the K-1 line by line against the underlying transactions.
Tip: When you receive your K-1, look at the line items individually before handing it to your personal preparer. If the corporation sold an asset during the year and you do not see a capital gain or a separate Section 1231 entry on your K-1, ask where it was reported before the corporate return is filed.
One of the most straightforward checks a CPA performs is also one of the most important. The total of every K-1 issued to every shareholder must equal exactly what is reported on Schedule K, line by line. Unlike a partnership, an S-corp allocates all items strictly pro-rata by stock ownership. There are no special allocations. Every shareholder receives the same percentage of every item, and the percentages across all shareholders must add to 100 percent.
According to the AICPA 2025 Form 1120-S Checklist, a discrepancy between Schedule K totals and the aggregate of all K-1s issued is one of the most common sources of IRS inquiries on S-corp returns. The IRS matches K-1 data reported on shareholders' personal returns against the Schedule K filed by the corporation. When those numbers do not align, automated notices follow.
This reconciliation sounds mechanical, but it is where allocation errors introduced earlier in the process surface. An incorrect ownership percentage, a mid-year ownership change handled using the wrong method, or a K-1 amended after Schedule K was finalized all produce a mismatch. A CPA confirms the reconciliation before the return is filed, not after.
Tip: If your S-corp had a shareholder join or exit during the year, ask your CPA specifically how the income was allocated between the departing and incoming shareholder and which method was used. The two available methods, daily proration and closing of the books, produce different results, and the choice affects what each shareholder reports on their personal return.
A CPA reviewing a Form 1120-S also examines shareholder basis, because the losses flowing through on each K-1 are only deductible on the personal return to the extent the shareholder has sufficient basis to absorb them. Beginning with the 2021 tax year, the IRS requires shareholders to complete Form 7203 to track stock and debt basis whenever they claim a loss, receive a distribution, dispose of S-corp stock, or receive a loan repayment.
The CPA's review confirms that basis has been tracked continuously from prior years, that the opening balance on the current year's Form 7203 matches the closing balance from the prior year, and that any distributions made during the year have been checked against the shareholder's available basis before being treated as tax-free. Distributions that exceed basis are capital gain, not a tax-free return of investment, and a shareholder who treats an excess distribution as tax-free has understated income on their personal return.
Tip: Basis tracking is a multi-year obligation. If the S-corp's first year of operation did not include a documented basis calculation, every subsequent Form 7203 is built on a flawed foundation. Correcting basis errors retroactively is possible but time-consuming. Catching and addressing them during the current year's preparation is significantly less expensive.
Schedule M-2 tracks the corporation's accumulated adjustments account, which is the pool of previously taxed earnings available for tax-free distribution to shareholders. A CPA verifies that the AAA opening balance matches the prior year's closing balance, that the current year's additions and reductions are calculated correctly, and that any distributions made during the year did not exceed the available AAA balance.
The AAA is reduced by ordinary losses, non-deductible expenses, and certain distributions, as well as increased by ordinary income and separately stated income items. A corporation that tracks only the income additions and ignores the reductions gradually overstates the AAA, and the error surfaces when a distribution is made that the account cannot actually support. That distribution then becomes a return of capital up to the shareholder's stock basis, and capital gain above it, producing a taxable event the shareholder did not expect.
Tip: The Schedule M-2 this year must open with the exact number from the closing balance of last year's Schedule M-2. If those two numbers differ and nobody can explain why, something went wrong in a prior year. The earlier that discrepancy is traced and corrected, the less expensive the fix.
A CPA also confirms that the S-corp election remains in effect and has not been inadvertently terminated. According to the IRS, an S-corp election terminates automatically when the corporation has more than 100 shareholders, admits an ineligible shareholder such as a non-resident alien or a disqualified trust, creates a second class of stock through distribution arrangements that give one shareholder preferential economic rights, or accumulates too much passive income for three consecutive years while carrying prior C corporation earnings and profits.
Any of these events reverts the corporation to C corporation status, and the IRS may not flag it immediately. A corporation operating under a terminated election is filing the wrong return, and the correction process is expensive and complicated.
Tip: If the S-corp added any shareholders during the year, admitted any trusts or estates to the ownership structure, or made distributions that treated some shareholders differently from others, confirm the eligibility status of each new owner and the economic character of each distribution before the return is filed. An inadvertent termination caught during preparation is far easier to address than one discovered during an audit.
Every check a CPA performs on a Form 1120-S has the same purpose: making sure that every K-1 issued to every shareholder is accurate, defensible, and consistent with both the corporation's financial records and the IRS requirements in effect for the current tax year. A return that passes each of these reviews does more than satisfy a filing obligation. It protects every shareholder's personal tax position and gives the corporation a clean foundation for the year ahead.
At TrueView CPA, S-corp tax return preparation and S-corporation tax filing services for business owners across Dallas and Texas are built around this review process. If you want confidence that your Form 1120-S was prepared correctly this year, or you are looking for a CPA for your 1120-S tax return preparation before the next March deadline, we are ready to start with a conversation.
Want a thorough review of your S-Corp return? Schedule a call with our tax experts today.
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