Google GOOG this afternoon reported that it easily topped Q3 revenue expectations, with $9.72 billion. It also reported that it has more than 40 million users of its Google+ social service, although it’s unclear how deep the average engagement is compared to that of Facebook users.

One of the more interesting items in Google’s release involves its tax bill. The search giant reports that its “effective tax rate was 19% for the third quarter of 2011.”

That’s in line with what Google paid in Q2, but down significantly from the 25% effective tax rate paid in Q1. For context, the highest U.S. corporate tax rate is 35% — while the average federal and state tax rate is a share above 39%.

It also comes as reports suggest that Google is being audited by the IRS for allegedly sheltering profits in offshore subsidiaries. Google did not mention the audit in its Q3 earnings release.