GAAP earnings per share is the net-income-based EPS figure a company reports in its financial statements under U.S. Generally Accepted Accounting Principles. Adjusted, or non-GAAP, EPS is a company-defined figure that starts from a GAAP number and adds back or removes items management considers not representative of ongoing operations — commonly stock-based compensation, acquisition and restructuring charges, amortization of acquired intangibles, and certain one-time gains or losses. The two can differ widely, and the SEC regulates how a company may present the non-GAAP version.

That regulation is Regulation G, which conditions any public non-GAAP disclosure on showing the comparable GAAP number alongside it.

"Whenever a registrant, or person acting on its behalf, publicly discloses material information that includes a non-GAAP financial measure, the registrant must accompany that non-GAAP financial measure with: (1) A presentation of the most directly comparable financial measure calculated and presented in accordance with Generally Accepted Accounting Principles (GAAP)."— SEC Regulation G (17 CFR 244.100), source

Regulation G adds a second requirement: a quantitative reconciliation of the differences between the non-GAAP measure and the most directly comparable GAAP measure. It also prohibits a non-GAAP measure that, taken with its accompanying information, is materially misleading. For filings and earnings releases furnished to the SEC, Item 10(e) of Regulation S-K layers on further conditions — the GAAP measure must be presented with equal or greater prominence, and certain adjustments (such as labeling a recurring cash charge as non-recurring) are restricted. Together, Regulation G and Item 10(e) mean a company is free to define an adjusted EPS, but not free to present it without the GAAP anchor and the bridge between the two.

Why the gap between the two numbers matters

GAAP EPS is comparable across companies because it follows a common standard; adjusted EPS is defined by each company and is not standardized, so two firms' “adjusted” figures may exclude different items. The reconciliation Regulation G requires is therefore the analytically important part: it itemizes exactly what was added back to get from GAAP to adjusted. A large and recurring add-back — stock-based compensation that appears every quarter, or amortization of intangibles that will persist for years — is an excluded real cost, and the reconciliation is what makes that visible. Reading adjusted EPS without reading the reconciliation discards the information the rule was written to preserve.

One further distinction helps when comparing companies: basic versus diluted EPS exists within GAAP itself, separate from the GAAP-versus-non-GAAP question. Basic EPS divides earnings by the weighted-average shares outstanding; diluted EPS additionally reflects securities that could convert into common stock, such as options, RSUs, and convertible notes, and is the more conservative figure companies are required to present alongside basic. Adjusted EPS is a third, non-GAAP layer applied on top of either. Keeping the two axes straight — GAAP basic and diluted on one hand, company-defined adjusted on the other — is what lets a reader place any headline EPS number in context and find, in the reconciliation, exactly how it was built.

It helps to see how a company actually gets from GAAP EPS to adjusted EPS. The starting point is GAAP net income attributable to common shareholders, divided by the weighted-average share count (basic) or by that count plus the dilutive effect of options, RSUs, and convertibles (diluted). To produce an adjusted figure, a company adds back items it characterizes as not reflecting ongoing operations and recomputes per share. The most common add-backs are stock-based compensation, amortization of acquired intangible assets, restructuring and severance charges, acquisition-related costs, impairments, and discrete tax items. The reconciliation Regulation G requires is the line-by-line bridge that shows each of these adjustments and its per-share effect.

The presentation rules are stricter for documents filed with the SEC than for general public statements. Item 10(e) of Regulation S-K, which applies to SEC filings, requires that the most directly comparable GAAP measure be presented with equal or greater prominence than the non-GAAP measure, requires the reconciliation, and prohibits certain practices — for example, describing a charge as non-recurring, infrequent, or unusual when a similar charge is reasonably likely to recur within two years or occurred in the prior two years. Earnings releases that companies furnish to the SEC on Form 8-K under Item 2.02 fall within this stricter regime, which is why a well-formed release leads with or gives equal prominence to the GAAP number and carries a reconciliation table.

The reason all of this matters to a reader is comparability. GAAP EPS follows a common standard, so it can be compared across companies; adjusted EPS is defined company by company, so two firms' adjusted figures may exclude different items and are not necessarily comparable to each other. A recurring add-back — stock-based compensation that appears every quarter, or intangible amortization that will run for years — is a real cost to shareholders that the adjusted figure removes. Reading the reconciliation is therefore not optional detail; it is the step that shows precisely what the adjusted number left out, and both the GAAP figure and the reconciliation are present in the company's filings on EDGAR.

None of this makes one measure correct and the other wrong; GAAP and non-GAAP EPS answer different questions, and the SEC's framework is about presentation and comparability rather than banning adjustments. For a reader, the practical rule follows the regulation: find the GAAP figure the company is required to show with equal prominence, then read the reconciliation to see precisely what the adjusted figure left out. Both numbers, and the reconciliation, appear in the earnings release furnished on Form 8-K and in the periodic report on EDGAR, which makes those filings the primary source behind any comparison of a company's reported and adjusted earnings.