What are the odds of winning a prize by completing the Taco Bell receipt survey?

According to Taco Bell, the odds of winning the Tell The Bell sweepstakes is dependent on the number of eligible entries received during the entry period. As of 2015, one winner is selected each period, which begins at 12:00 a.m. CST each Wednesday and ends 11:59 p.m. the following Tuesday.

The winner of the $500 prize is selected from eligible online and mailed entries within approximately five weeks from the end of each entry period. The winner of the customer survey sweepstakes is notified by email, postal mail and/or telephone within approximately six weeks after the end of the entry period.