Collectors bills are sometimes offered for doing searches through swagbucks. If you use the 'search the web' box at the top left of the homepage to search, SB randomly assigns points for searching (from what I have read, you can get search points about 4 times during a day). When they are also offering collectors bills for searches, there is an extra bonus for getting all the bills. I usually do not succeed because I get multiples of some bills. If you go to the drop down box on the upper right by your total SB, and click on activity, there is also a box there to see the collectors bills you have.