Introduction
On January 1, 2025, Amazon shortened the depreciable life of part of its servers and networking equipment from six years to five, citing the pace of technological change in artificial intelligence (AI). The change raised its 2025 depreciation by $1.4 billion and cut net income by $1.0 billion, or $0.10 a share, as its 2025 annual report discloses. Nothing earlier was restated; the new estimate simply applied from that date.
A year earlier, Archer-Daniels-Midland had found errors in how it recorded sales between its own segments, mostly involving its Nutrition business. The errors did not change ADM's consolidated revenue or profit, but they misstated the segment results investors used to value that business. ADM corrected its segment disclosures, reported a material weakness in internal control and later amended its annual report to restate the segment information, as its amended 2023 annual report describes. Its January 2024 announcement of an internal investigation came with its chief financial officer placed on leave and a sharp fall in its share price. The two cases sit at opposite ends of the rules in Accounting Standards Codification (ASC) 250, which distinguish three kinds of change: changes in estimate, changes in principle and corrections of errors.
Changes in Accounting Estimates
Accounting is full of estimates: useful lives and salvage values, credit losses, warranty costs, inventory reserves, the costs to complete long-term contracts, pension assumptions, the fair value of unlisted investments. When new information changes an estimate, the effect is recognized prospectively, in the period of the change and in future periods, without restating the past.
- Change in accounting estimate
A revision of an amount resulting from new information or developments, such as a change in the expected useful life of equipment or the collectibility of receivables. Under ASC 250 it is accounted for prospectively, and its effect on income and earnings per share is disclosed when material.
The prospective treatment makes sense: an estimate made in good faith with the information available was not wrong, even if hindsight improves on it. But it also means that changes in estimate move current earnings without any change in the business, and that a favorable change shows up as improved profitability rather than as an adjustment. Amazon's change reduced its earnings; the reverse, lengthening useful lives, raises them. In 2022 and 2023, several large technology companies had extended server lives, adding billions to operating income, before the AI investment cycle began to push lives in the opposite direction, the debate examined in useful lives under scrutiny.
The disclosure requirement is the analyst's tool. When an estimate change is material, the company must disclose its effect on income from continuing operations, net income and earnings per share, which allows the effect to be removed for comparison with earlier periods. Where a company changes several estimates in the same direction in the same year, or changes them in a year when results would otherwise disappoint, the pattern deserves the attention described in accounting red flags.
Changes in Accounting Principle
A change in accounting principle is a switch from one acceptable method to another, such as from last-in, first-out (LIFO) to first-in, first-out (FIFO) inventory costing. It is applied retrospectively: prior periods presented are restated as if the new principle had always been used, unless that is impracticable, with the cumulative effect on periods before those presented recorded in opening retained earnings. A voluntary change must be justified as preferable, and Securities and Exchange Commission (SEC) registrants file a letter from their auditor, the preferability letter, confirming that the new method is preferable in the circumstances.
New Standards and Transition Methods
Most changes in principle come from new accounting standards rather than choice. Each new standard sets its own transition method: some require full retrospective restatement, others allow a modified approach that applies the standard from the adoption date with a cumulative adjustment to retained earnings, leaving earlier periods unchanged. The method matters for analysis, because under a modified approach the first year after adoption is not comparable with the year before. The leases standard and the revenue standard were both adopted by many companies on that basis.
A change in the reporting entity, for example when a company changes the subsidiaries it consolidates for reasons other than an acquisition or disposal, is also applied retrospectively, so that the financial statements show the same entity across all periods presented.
Corrections of Errors
An error is a mistake in recognition, measurement, presentation or disclosure, whether from a mathematical slip, a misapplication of the rules or the oversight or misuse of facts that existed at the time. How it is corrected depends on whether it is material to the previously issued statements.
Materiality is judged on both quantitative and qualitative grounds under SEC staff guidance. An error that is small in amount can still be material if it turns a loss into a profit, hides a change in trend, affects compliance with a covenant or concerns a segment investors rely on, as ADM's did: its errors left consolidated profit untouched, yet in November 2024 the company filed an Item 4.02 notice that its earlier financial statements should no longer be relied upon, and restated the segment note. Errors that have accumulated over several years are assessed both on their effect in each year and on the cumulative misstatement in the current balance sheet.
The three kinds of change compare as follows:
| Type | Example | How it is reported | Prior periods restated? |
|---|---|---|---|
| Change in estimate | Shorter useful lives for servers | Prospectively, with disclosure of the effect | No |
| Change in principle | Switching from LIFO to FIFO | Retrospectively, with an auditor's preferability letter if voluntary | Yes, unless impracticable |
| Correction of an error | Misclassified intersegment sales | Big R restatement or little r revision | Yes |
Clawbacks and the Cover Page
Restatements carry consequences beyond the accounts. Since 2023, under the SEC's Rule 10D-1, listed companies must have clawback policies to recover executives' incentive-based compensation that was paid on the basis of figures later restated, and the rule covers both Big R and little r corrections. The cover page of the annual report now carries two checkboxes indicating whether the financial statements include a correction of an error and whether any correction required a recovery analysis under the policy.
What a Restatement Signals
A restatement is one of the strongest signals in financial reporting, because it is an admission that previously issued figures were wrong. Big R restatements are often accompanied by material weaknesses in internal control, changes in management or auditors, regulatory investigations and litigation, and markets usually react sharply. Little r revisions are more common and less serious, but a pattern of them suggests weak controls.
For bankers, the practical effects are immediate. Figures from periods under restatement cannot be used in offering documents until corrected, which can delay a financing or a deal; auditors will need to deliver comfort letters to underwriters on the restated numbers; and valuation work, including trailing twelve months figures built as described in LTM figures from filings, must use the restated amounts. In acquisitions, a target's restatement history is a diligence priority, and a material weakness can change the protections a buyer negotiates.
Changes in estimate, finally, are worth tracking even when nothing is restated. They are the most common way for reported earnings to move without any change in operations, and the disclosures that quantify them are among the most useful sentences in the notes for anyone trying to separate the business from the accounting.
