After much talk the past few months about concerns over non-GAAP reporting among public companies, the Securities and Exchange Commission has taken more formal action to warn companies to be careful.

The SEC updated its Compliance & Disclosures Interpretations guidance with a dozen new questions and answers focused on how companies might report financial information that falls outside the realm of Generally Accepted Accounting Principles without also running afoul of financial reporting requirements. SEC Chair Mary Jo White recently contemplated the possibility that the SEC might issue guidance to “rein in” use of non-GAAP measures, and James Schnurr, chief accountant at the SEC, also has urged more caution.

Non-GAAP reporting is not expressly forbidden under SEC rules, but companies are required to follow Regulation G to assure they are using non-GAAP measures in a way that is informative and not misleading. The first Q&A in the SEC’s latest guidance addresses that very fact.

Yes, the SEC says, it’s possible to contrive a non-GAAP measure of financial performance that is not explicitly prohibited, but is still misleading to investors. One such example, the guidance says, is presenting a performance measure that excludes normal, recurring, cash operating expenses.

Don’t try to tell investors, for instance, that you would have earned more during a particular period if not for non-cash compensation paid to executives. Chuck Mulford, executive director of the Georgia Tech Financial Analysis Lab recently called that out as a clear abuse.

Recent studies have pointed out a surge in public company reporting of non-GAAP measures to their investors. A Georgia Tech analysis said three out of four companies in the S&P 100 reported earnings on a non-GAAP basis in 2013. Another analysis by investment firm R.G. Associates says 401 of the S&P 500 companies reported non-GAAP net income in 2015 compared to 269 companies in 2009.

And companies reporting non-GAAP income are reporting better numbers, R.G. Associates said. GAAP earnings for 380 companies in the S&P 500 fell 10.9 percent from 2014 to 2015, but non-GAAP adjustments at the same companies produced non-GAAP earnings that increased 6.6 percent. Adjustments in 2015 represented the highest level of non-GAAP adjustments since 2009, almost double the level of just one year earlier, the report said.

In addition to caution on misleading non-GAAP adjustments, the new SEC guidance tells through a Q&A format that companies need to be consistent in their use of non-GAAP measures from one period to the next or be prepared to provide disclosure on why a particular measure is relevant one period when it wasn’t earlier. Consistency is also important in terms of non-recurring charges as well as non-recurring gains, the guidance says.

The latest SEC guidance addresses numerous other aspects of non-GAAP reporting, including adjustments that accelerate revenue recognition, adjustments involving funds from operations, measures that eliminate or smooth over items identified as non-recurring or unusual, items expressed on a per-share basis, presentation of free cash flow, comparability of GAAP and non-GAAP presentations, adjustments for income tax effects, and reconciling the common-non-GAAP measures of EBIT or EBITDA.

Organizations like PwC and Credit Suisse also are publishing alerts to companies to make sure their use of non-GAAP measures is compliant with the current requirements.