use INIT which will overwrite the previous
INIT
Specifies that all backup sets should be overwritten, but preserves the media header. If INIT is specified, any existing backup set data on that device is overwritten
TSQL would like this:
BACKUP DATABASE [DBNAME]
TO [BACKUPDEVICE]
WITH INIT ,
NOUNLOAD ,
NAME = N' RentRoll',
NOSKIP ,
STATS = 10,
NOFORMAT
hope this helps