SAN FRANCISCO — Talk about a caffeine jolt. When securities regulators questioned whether Green Mountain Coffee Roasters had improperly booked sales, investors unceremoniously dumped the stock down the drain.

The high-flying shares lost 20 percent of their value within a week following the late September news of the Securities and Exchange Commission probe. The sell-off shaved $1 billion from the market value of the fast-growing coffee company that sells the Keurig single-cup coffee machines and the coffee brewed in them.

Green Mountain hasn’t been charged with any wrongdoing, but the stock hasn’t yet recovered from the beating.

How a company accounts for sales can be a gray area of a financial statement, challenging an investor’s ongoing efforts to give a company’s earnings a thorough examination.

Accordingly, it’s crucial to watch for changes to the “revenue recognition” policy a company uses. This policy can be found in the “critical accounting policies” section of a company’s annual and quarterly reports, which are filed with the SEC.

Besides checking on revenue recognition, there are other clues that a company is possibly manipulating sales:

• Compare policies: When looking at one company, check on another that makes or sells similar products. The key is to see which company within an industry sector appears to be more aggressive in recording sales.

This is because all companies will phrase their revenue recognition policy so “it sounds right,” said Tom Robinson, managing director for education at the CFA Institute, a global association of investment professionals.

“The earlier in the process they book a sale, the less conservative they are,” Robinson said.

• Days sales outstanding: It’s also important to check if a company is getting looser with its credit terms or offering other incentives to push more product onto its retailers.

To find out, calculate the days sales outstanding. This measures how fast a company is collecting revenue after a sale has been marked on the books.

To calculate days sales outstanding on a quarterly basis, multiply total receivables by 91.25 days. Then divide that result by sales for the current quarter.

If the resulting number is two to three days higher than the previous year’s quarter, this could be a clue that a company is getting more aggressive, said Bill Whiteside of Behind The Numbers, a research firm that scrutinizes balance sheets for aggressive accounting.

Yet be aware that a higher days sales outstanding number does not always prove accounting shenanigans.

For instance, days sales outstanding can increase if a company made an acquisition or is experiencing accelerated sales growth. So further fact-digging is required before drawing any conclusions, he said.

• Deferred revenue: Deferred revenue is another place to check for sales discrepancies on a company’s books. It can be found on the balance sheet under the liabilities section.

Deferred revenue is money collected before a company ships its product. It is considered a liability until the revenue is recognized on the income statement.

Normally, you want to see deferred revenue and sales growing at roughly the same pace.

Here’s what to watch out for: If the amount of deferred revenue being reported each quarter is growing at a slower rate than sales growth, this may be a sign a company is closing fewer deals and future revenue will wane.

• Unbilled receivables: Look out for a sharp jump in unbilled receivables, which are listed in the current assets section of the financial statements.

These are long-term contracts under which a company agrees to perform work over a length of time and periodically bills the customer for completed work.

Here’s the catch: Under U.S. accounting rules, it is possible for a company to report the sale on its financial statement before it is even paid for the work.