It’s only based on the rent of December and how long you lived in there doesn’t count for anything. If you lived in a place from Jan. to October and moved out on November, you won’t get a tax receipt from that place. Also if your rent on Dec. 2003 is $500 and another tenant’s rent is also $500, your rent on Dec. 2004 is $510 and another tenant’s rent is $520 that can cause the decrease of your tax receipt for 2004. I hope that this explains the difference to you!