Airbnb has raised $555 million during a funding round, documents filed with the Securities and Exchange Commission (SEC) show.

In August, rumors surfaced about the company filing official documents with the State of Delaware, which revealed Airbnb's aim to attract more late-stage capital.

The Form D filed on Sept. 23 backs the story, but insiders familiar with the matter are pointing out that Airbnb is far from closing the round. According to sources, the company might push the ceiling to a figure of $850 million.

It is rather standard procedures for ventures to file with the SEC preemptively, maintaining a flexible ceiling so that final deal terms can be tweaked as the funding round is still undergoing.

It is yet undisclosed if the company maintains its initial valuation of $30 billion. Should this be the case, it could lead to modifications in the price of the round. A more pragmatic and down to earth valuation will become available after the deal is formally closed.

Keep in mind that, should the initial valuation be proven correct, Airbnb would become the fourth most valuable private startup.

A myriad of strategic investors is part of the recent deal, people close to the matter are reporting.

The company is far from lacking cash, but the eight-year-old venture might be starting to be under pressure from employees who are unable to cash in on common stock.

Additional pressure is perceivable from early-stage investors, who are eager to tap into liquidities coming from the Airbnb's mounting success.

The additional capital drawn in the recent round will help the company expand and will ease some of the pressure the company is under, as it still postpones an initial public offering (IPO).

The Wall Street Journal reports that Airbnb is being aided in the funding by Technology Crossover Ventures (TCV) and Google Capital. Additional rumors indicate that no employees of Google Capital nor of TCV will join Airbnb's board. As both investors are new to the home-sharing company, their efforts will coagulate around helping the enterprise grow.

The funding round happens amid a number of legal disputes between the company and various authorities.

Airbnb is currently in court with the City of San Francisco. What is more, the city council of Barcelona asks its residents to rat out illegal rentals (aka Airbnb offerings).

Despite having enough cash to keep going, the fact that a number of municipalities (including New York) are still uneager to approve home-sharing services does not make Airbnb's life any easier.