Groupon, the online coupon site that recently turned down a $6 billion acquisition offer from Google (GOOG), has raised $500 million in venture capital funding, according to a filing with the SEC.

No new board members are listed, meaning that we do not know the identities of participating investors. Other media reports, however, have suggested that new backers include Morgan Stanley (good way to get the inside track for an IPO), T. Rowe Price and Fidelity.

Digital Sky Technologies, which led the company’s $135 million Series C round this past spring, also is believed to be heavily involved.

Groupon’s SEC filing indiates that the company still plans to raise upwards of another $450 million, which it first disclosed via an ammended certificate of incorporation. It is worth emphasizing, however, that the $950 million “offering amount” may represent an upper limit to the investment, rather than a target (sometimes companies list artificially-high numbers, in order to provide financial/accounting flexibility).

Groupon CEO Andrew Mason so far has declined to discuss the new funding, beyond the following Tuesday tweet:

Groupon is in the process of completing a new round of financing – we’ll let everyone know when there’s more to announce.

One purpose of Groupon’s massive new round is to provide liquidity for existing shareholders, including those who may have been ticked off that the company spurned Google. Fortune has learned that all Groupon shareholders recently received a letter offering to buy back up to 15% of current stock holdings, and the SEC filing indicates that $345 million of the $500 million will be used to cash out insiders (both investors and management).

In addition to DST, Groupon previously raised venture capital from firms like Accel Partners, Battery Ventures, New Enterprise Associates and a whole host of individuals.

What is yet to be seen is if this will go down as the largest venture capital deal of all time. Most industry trackers only include “new equity” in their calculations, which would shrink the current Groupon raise from $500 million to just around $155 million. Still a large number, but nowhere near an all-time record. For example, movie studio DreamWorks (then a startup) raised $500 million from Paul Allen’s Vulcan Capital in 1995. Moreover, both Better Place ($350m) and Twitter ($200m) have raised large “new equity” rounds just this past year.

Were Groupon to raise another $450 million of “new” equity, however, then it would indeed be the largest round (according to MoneyTree, a consortium that includes PwC, the National Venture Capital Association and Thomson Reuters).

In terms of total venture capitalization, Groupon would come in at around $776 million (including the new $450m, excluding the cash-out). According to a Business Insider analysis from this past summer, that would put Groupon fourth on the all-time list.