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For silent auctions which include a capital fund raiser by raising a paddle, Pearl Bids silent auction software supports entering mutiple offers at the same price. 
For a 'Raise the paddle' you can make a couple of donation items.  eq 'Raise the paddle $500', 'Raise the paddle $250', 'Raise the paddle $100'. Set the 'Number of Donations" to the number of paddles you are expecting (you can change this anytime*) and set the "Donation Type" to  "Each bidder is a winner".
 
If you have a have a bidding license, you can enter the wining paddles in as you would  any other bid, up to the 'Number of donations'. These bids will be included on the bidder's receipt as well. 
 
Tip: The printed bid sheet includes your first 10 bidders. Why not put these bidsheets on the table as well? It gets people used to the idea, and guests who might have to leave early a chance to participate.  
 
* Don't overdo the number of expected bids, as these are included in your total marketvalue for your auction.