Ah, DC. Which other jurisdictions so obsessively track you and force you to show papers proving you don't live there?
While parked legally on a street in DC this weekend, I received a warning notice for failure to register for DC tags. Since I already pay car tax as a resident of Virginia, DC can go jump in a lake. However, telling them to do so is going to be something of a pain. In order to not incur a $100 ticket, you must report to the DC DMV and prove you live elsewhere with your original lease, a recent utility bill, and your car registration. (In return, they will give you a six-month exemption, at the end of which the entire process repeats itself.) You can also mail this information to them, but the ticket also helpfully notes that the processing period associated with doing so may exceed the fifteen day grace period before which a ticket for failure to register is issued.
In contradiction to both this blog post on the problem and the DMV's own website, which make it sound like you only get these for parking twice within thirty days, the warning notice clearly states that "[y]our vehicle has been observed for the second time within a 180 day period parking without DC tags." So if you've parked in DC while shopping, visiting a friend, or doing business within the last six months, beware of that second trip. And heaven help you if you don't have a lease or mortgage or have your name on the utilities.