The auditor of a US public company is an independent registered public accounting firm that audits the annual financial statements and signs an opinion on them, and its work can be seen in the filings: the audit report printed in the 10-K, an internal control attestation for larger filers, and an 8-K whenever the firm changes. Among the 791 roster 10-Ks whose cover page carries the flag, 618 say the auditor attested to internal control, and in 2026 the record holds 331 original Form 8-K reports under Item 4.01 in which a company changed the firm.

All of that work is on sec.gov. The audit report sits inside the 10-K, next to the financial statements it covers. The attestation is flagged on the 10-K cover. A change of firm gets its own 8-K within four business days. This guide follows the auditor through each of those documents, using 3M Company's 10-K for 2024 as the worked example and the record's own counts for the rest.

The firm, and the board it answers to

The auditor is a firm, never a person. The audit report is signed in the firm's name ("/s/ PricewaterhouseCoopers LLP" in 3M's case), and the report states that the firm is registered with the Public Company Accounting Oversight Board. Registration is what makes it a "registered public accounting firm" in the language of the rules, and only a registered firm can sign the opinion that goes into a public company's annual report.

The firm does not report to the chief financial officer. Exchange Act Rule 10A-3 puts the relationship with the audit committee:

Figure 1: annotated excerpt

“must be directly responsible1 for the appointment, compensation, retention and oversight2 of the work of any registered public accounting firm engaged”
  1. 1The duty sits with the audit committee of a listed issuer, acting as a committee of the board, not with management.
  2. 2Four powers: hiring the firm, setting its fee, keeping or replacing it, and supervising its work.
Verbatim, from govinfo.gov.

The same paragraph says the firm "must report directly to the audit committee" and that the committee resolves "disagreements between management and the auditor regarding financial reporting." Management prepares the statements. The committee hires the firm that checks them. The finance team works with the auditor every day, but the engagement letter, the fee and the decision to keep or replace the firm belong to the committee.

What the auditor reports on

Regulation S-X Rule 2-02 sets the minimum for an accountant's report on financial statements filed with the SEC. The report "shall be dated," "shall be signed manually," "shall indicate the city and State where issued," and shall identify the financial statements it covers. It "shall state the applicable professional standards under which the audit was conducted," and it "shall state clearly" two opinions: one on the financial statements and one "as to the consistency of the application of the accounting principles."

3M's report for 2024 shows each of those pieces in order. It opens by naming what was audited: the consolidated balance sheet at December 31, 2024 and 2023 and the statements of income, comprehensive income, changes in equity and cash flows for three years. Then the opinion paragraph:

Figure 2: annotated excerpt

“In our opinion1, the consolidated financial statements referred to above present fairly, in all material respects2, the financial position of the Company as of December 31, 2024 and 20233”
  1. 1The opinion comes first in the report, before the basis for it.
  2. 2The standard wording of an unqualified opinion. The report does not say the numbers are exact; it says they are fair in all material respects.
  3. 3The balance sheet dates covered. The income and cash flow statements are covered for each of the three years in the period.
Verbatim, from sec.gov.

A second sentence in the same paragraph gives the opinion on internal control: "the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2024." That sentence appears only because 3M is a large accelerated filer, which brings in the attestation requirement described below.

After the opinions comes "Basis for Opinions," which states that the audits were conducted "in accordance with the standards of the PCAOB" and describes the work: procedures to assess the risk of material misstatement, "examining, on a test basis, evidence regarding the amounts and disclosures," evaluating the accounting principles and the significant estimates. Then a section on critical audit matters, which 3M's report defines in its own words as matters "communicated or required to be communicated to the audit committee" that relate to material accounts or disclosures and "involved our especially challenging, subjective, or complex judgments." The report says plainly that describing them does not alter the opinion. 3M's first one is its PFAS-related legal proceedings, with the procedures the firm ran listed beneath it.

The report ends with the signature, the place and the date, and one more sentence:

Figure 3: annotated excerpt

“/s/ PricewaterhouseCoopers LLP1 Minneapolis, Minnesota2 February 5, 20253 We have served as the Company’s auditor since 1975.4”
  1. 1The firm's conformed signature. Rule 2-02(a) requires the report to be signed manually; the filed copy shows the signature as /s/.
  2. 2The city and State where the report was issued, as Rule 2-02(a)(3) requires.
  3. 3The report date, which is also the day the 10-K was filed with the SEC here.
  4. 4The tenure statement. It gives the first year of the engagement, the one place in the 10-K where the length of the relationship is printed.
Verbatim, from sec.gov.

Where the report sits in the 10-K

Form 10-K puts the financial statements in Item 8, and the auditor's report goes with them. In practice the report opens Item 8, under the heading "Report of Independent Registered Public Accounting Firm." In 3M's 10-K it runs from page 42 to page 44, directly after management's report on internal control and directly before the consolidated statement of income. A search of the 10-K text for "Independent Registered Public Accounting Firm" finds it in seconds.

Two other places in the 10-K point to the audit. The cover page asks whether the registrant has filed a report on and attestation to management's assessment of internal control "by the registered public accounting firm that prepared or issued its audit report," with a check box. And Item 9A, Controls and Procedures, carries management's own report on internal control under Regulation S-K Item 308. When the auditor has attested, Item 308(a)(4) requires management to say so, and 3M's Item 9A does: its internal control "has been audited by PricewaterhouseCoopers LLP, an independent registered public accounting firm, as stated in their report which is included herein."

The fees come later. Item 14 of the 10-K, Principal Accountant Fees and Services, asks for "the aggregate fees billed for each of the last two fiscal years" by the principal accountant, under captions that begin with Audit Fees. 3M, like many large filers, incorporates Part III, Items 10 through 14, by reference from its proxy statement, so the fee table is printed there.

The second opinion: internal control

Item 308(b) requires the auditor's attestation report on internal control for a registrant that is an accelerated filer or a large accelerated filer, "other than a registrant that is an emerging growth company." Rule 2-02(f) puts the matching duty on the firm. A non-accelerated filer still files management's report under Item 308(a) and still has its financial statements audited; what it does not need is the auditor's opinion on internal control.

That split shows up cleanly in the roster. The 10-K cover carries the answer as tagged XBRL data, the ICFR Auditor Attestation Flag, and the record read it from the cover page of each roster seat's 10-K.

Figure 4

618 roster 10-Ks say on the cover that the auditor attested to internal control

618 roster 10-Ks say on the cover that the auditor attested to internal control. Roster 10-Ks: Large accelerated filer: Auditor attested to internal control 574, No auditor attestation 5; Accelerated filer: Auditor attested to internal control 42, No auditor attestation 1; Non-accelerated filer: Auditor attested to internal control 1, No auditor attestation 110; not established: Auditor attested to internal control 1, No auditor attestation 57.Auditor attested to internal controlNo auditor attestation0150300450600579Large accelerated filer43Accelerated filer111Non-accelerated filer58not establishedFiler categoryRoster 10-Ks
Roster 10-Ks whose XBRL cover page could be read, by the filer category EDGAR reports, split by the cover's ICFR auditor attestation flag. Source: CFO Tribune roster record (verified 10-K signature seats); the filing index, Exhibit 31 and 32 documents and XBRL cover page (R1.htm) of the 10-K each verified roster seat cites, read once each from sec.gov; category from the EDGAR submissions JSON (data.sec.gov), read once per company. As of November 11, 2026.

Of the 791 10-Ks with a readable flag, 618 say the auditor attested and 173 say it did not. Among large accelerated filers, 574 of 579 carry the attestation. Among non-accelerated filers, 110 of 111 do not, which is what the rule predicts. Accelerated filers carry it in 42 of 43. The largest group without it, after the non-accelerated filers, is the 57 companies for which EDGAR reports no accelerated or non-accelerated status, and there the emerging growth company exemption shows: 80 of the 81 emerging growth companies with a readable flag report no attestation, whatever their size.

The flag is what the company tagged, read on the day of the pass; this guide does not test whether each answer was right. The category is EDGAR's current one, which can differ from the box checked on the 10-K itself. The filer status guide sets out how the categories are decided.

How the auditor is chosen and replaced

Because the audit committee is "directly responsible" for the appointment and retention of the firm, a change of auditor is a committee decision, and the company has to report it. Form 8-K Item 4.01 is the item. Within four business days of the old firm resigning, declining to stand for re-appointment or being dismissed, or of a new firm being engaged, the company files an 8-K that states what happened, whether the committee approved it, whether there were disagreements with the former firm, and whether the old firm's reports carried an adverse opinion or a disclaimer of opinion.

A typical report reads like this one, from Hornbeck Offshore Services, Inc., filed September 2, 2026:

Figure 5: annotated excerpt

“On September 2, 2026, the audit committee1 (the “Audit Committee”) of the Company’s board of directors approved the dismissal2 of KPMG as the Company’s independent registered public accounting firm, effective as of September 2, 20263.”
  1. 1The body Rule 10A-3 makes responsible for the engagement, named as the one that acted.
  2. 2The filing's own verb. Item 4.01 asks whether the former firm resigned, declined to stand for re-appointment or was dismissed, and the filing says which.
  3. 3The date of the change, which starts the four business day clock for the 8-K.
Verbatim, from sec.gov.

The record counts every Item 4.01 report it holds. In 2026, through November 6, there are 361 filings from 326 companies: 331 original reports and 30 amendments, 24 of which link the former firm's Exhibit 16 letter.

Figure 6

Between 20 and 59 original Item 4.01 reports in every full month of 2026

Between 20 and 59 original Item 4.01 reports in every full month of 2026. Original 8-K reports: Jan: 35; Feb: 21; Mar: 59; Apr: 46; May: 26; Jun: 38; Jul: 30; Aug: 20; Sep: 27; Oct: 27; Nov: 2.01530456035Jan21Feb59Mar46Apr26May38Jun30Jul20Aug27Sep27Oct2NovMonth filed, 2026Original 8-K reports
Original Form 8-K reports under Item 4.01 in the record, by month filed, January 1 to November 6, 2026. Amendments are left out. November is a partial month. Source: CFO Tribune disclosures record (verified Form 8-K Item 4.01 and 4.02 records, each linked to its sec.gov filing). As of November 11, 2026.

March is the high point, with 59 original reports. It is also the month when most calendar-year companies have just filed their 10-K, so the old firm's last opinion is signed and the new firm has the whole year ahead of it. The Item 4.01 study breaks the same filings down by how the engagement ended and how fast the 8-K followed.

The filings also show who acted, at least in the words the record quotes from them.

Figure 7

195 of 331 change reports name the audit committee in the words the record quotes

195 of 331 change reports name the audit committee in the words the record quotes. Original 8-K reports: Audit committee named: 195; Board named, no audit committee: 53; Neither named in the quoted words: 83.Audit committee named195Board named, no audit committee53Neither named in the quoted words83Original 8-K reports
Original Item 4.01 reports filed in 2026, by whether the filing language the record quotes names the audit committee, names only the board, or names neither. Source: CFO Tribune disclosures record (verified Form 8-K Item 4.01 and 4.02 records, each linked to its sec.gov filing). As of November 11, 2026.

In 195 of the 331 original reports, the quoted language names the audit committee. In 53 it names the board of directors and not the committee; in some of those the committee acted and the quoted sentence credits the board, and some small filers have no separate committee at all. In 83 the quoted words name neither. That is a limit of the count, not of the filings: the record quotes a few sentences from each report, and Item 304 asks the committee question in its own paragraph, which the record does not always quote. The list of auditor changes links each report so the full text can be read.

What the auditor cannot do

Independence is the condition for signing. Regulation S-X Rule 2-01 says the Commission "will not recognize an accountant as independent" if the accountant is not, or a reasonable investor with knowledge of all relevant facts would conclude the accountant is not, "capable of exercising objective and impartial judgment on all issues encompassed within the accountant's engagement."

The rule then lists services that end independence when the firm provides them to an audit client during the engagement period. Paragraph (c)(4) names ten: bookkeeping or other services related to the client's accounting records or financial statements; financial information systems design and implementation; appraisal or valuation services, fairness opinions or contribution-in-kind reports; actuarial services; internal audit outsourcing; management functions; human resources; broker-dealer, investment adviser or investment banking services; legal services; and expert services unrelated to the audit. The practical result for a finance team is that the firm that audits the statements cannot also keep the books, build the general ledger system or run internal audit.

Rule 2-01(c)(6) adds partner rotation. The lead partner and the engagement quality reviewer may not serve the same client "for more than five consecutive years," with a five-year break before returning. The firm can stay for decades, as 3M's tenure statement shows; the partners who run the audit change.

How often the relationship changes

The record does not yet hold a count of all public companies, so it gives no rate of auditor change. What it can say is narrower. Of the 831 companies on the roster, 33 filed an Item 4.01 report in 2026 that the record holds. Most roster companies kept their firm this year, and the tenure statements in their 10-Ks show engagements that run back decades in many cases.

The record does not count tenure. The plan for this guide called for a chart of how many former auditors had served two or more fiscal years, read from the dates the 8-K prints, but the record quotes the period sentence from too few reports for a count: 42 of the 2026 reports carry a "fiscal years ended" phrase in the quoted words. That chart waits until the disclosures desk records the period as a field.

Five things to check in any 10-K

  1. The report heading and signature. Find "Report of Independent Registered Public Accounting Firm" in Item 8 and read the signature line: the firm, the city and the date.
  2. The opinion wording. "Present fairly, in all material respects" is an unqualified opinion. Any other wording, a paragraph that begins "Except for," or an explanatory paragraph on going concern, changes what the report says.
  3. The tenure sentence. "We have served as the Company's auditor since" gives the first year of the engagement.
  4. The cover check box and Item 9A. Whether the auditor attested to internal control, and management's own conclusion on whether internal control is effective.
  5. The 8-K history. On the company's EDGAR page, any 8-K with Item 4.01 marks a change of firm, and its Exhibit 16 is the former firm's letter saying whether it agrees with what the company wrote.

Method

  • Audit report. 3M Company's 10-K for the fiscal year 2024, filed February 5, 2025, read once from sec.gov. The excerpts are verbatim.
  • Attestation flag. For each verified roster seat, the XBRL cover page (R1.htm) of the 10-K the seat cites, read once from sec.gov through the site's EDGAR client in November 2026. The flag is the cover's "ICFR Auditor Attestation Flag"; filer category is the category field of EDGAR's submissions file, as in the filer status guide.
  • Item 4.01 counts. Every verified Item 4.01 record filed from January 1 to November 6, 2026. Original reports are Form 8-K; amendments are Form 8-K/A. "Names the audit committee" is a plain text test on the filing language the record quotes.
  • Rules. Rules 2-01 and 2-02 of Regulation S-X, Item 308 of Regulation S-K and Rule 10A-3, from the 2025 edition of Title 17 on govinfo.gov, and Form 10-K from sec.gov.
  • Recomputing. scripts/articles/fetch-roster-exhibits.mjs reads the cover pages and saves what it read; node scripts/articles/compute.mjs --only auditorRole turns that and the record into every figure here.