Chart of the day: Apple’s hidden revenue stream

FORTUNE — Until I read Daniel Eran Dilger’s piece on Apple’s deferred earnings Friday in AppleInsider I’d forgotten what a big deal these hidden earnings were just a few years ago.

Dilger explains with admirable clarity why Apple (AAPL) has been holding some revenue in reserve each quarter to account for such things as AppleCare, iTunes gift cards and free software.

“Apple’s deferred revenues began rapidly building,” he writes, “when the company initiated ‘subscription accounting’ in 2007 with the release of the original iPhone, a practice that set aside a portion of new income that the company did not officially, immediately recognize it in its earnings reports, even though the company had collected the money.

“Instead, Apple incrementally recognized a fraction of that deferred revenue each quarter over a two year period. The practice was designed to ensure that revenue wasn’t counted ahead of delivering a full product, because in Apple’s accounting, the iPhone wasn’t finished until two years of software updates had been provided to the end user.”

I wrote quite a bit about Apple’s deferred revenue — and Wall Street’s failure to wrap its head around it — from early 2008 to late 2009, when the U.S. government’s accounting rules changed. See, for example, Spotlight on Apple’s hidden revenue stream and An accounting rule in Apple’s favor.

The issue popped back in the news this week — and Dilger was writing about it again — because Apple announced Monday that the company expects its deferred revenue in the current quarter to be a bit larger than usual to account for the fact that OS X and iWorks are now free.

About $900 million larger.

That’s in addition to the more than $10 billion in deferred revenue that Apple was already sitting on as of Sept. 29.

$10.96 billion is no small change. It’s more, as Dilger can’t resist pointing out, than Samsung earned last quarter ($8.2 billion). It’s three times what Google (GOOG) earned ($3.4 billion).

“Incredibly,” Dilger writes, “none of Apple’s critics in the tech media, or even in mainstream financial reporting circles, seems to realize this pool of billions even exists.”

That’s not entirely true. Analysts may disagree about the significance of the $900 million increase, but at least they’re talking about it. (See What the analysts are saying.)

Which is more than they were doing in 2008 and 2009.

Dilger’s piece: Apple now sitting on $10B in deferred revenue, more than Samsung or Google earned last quarter.

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