Starting in October 2008, the tax rate is going from $5 per $100 of the assessed value to $10 per $100 of the assessed value for vacant properties. (It still has to be approved by Fenty and Congress to become a permanent increase but STILL!) DC Gov implemented this "temporary" change early this year to increase it's coffers .
For the last several months, DC agents have been keeping a close eye on the legislation. Why do we care about this factoid? Because it can really mess up a closing! For example, if I'm representing any new construction condos, houses that have been renovated or sellers that have moved into their new property and are selling their old property, they can be hit with this vacancy tax. Non vacant properties are taxed at $.85 per $100 of the assessed value. That's a BIG difference. There are many exceptions to the rule BUT that means you have to gather paperwork and take the time to interact with DC Gov. Booo.
Check out the article from The Washington Business Journal: http://washington.bizjournals.com/washington/stories/2008/06/02/daily36.html?surround=lfn