MSSQL: Maintenance plan is not deleting the backup files

There are a few reasons that this task may fail, but one of the most common is the follow:
In Maintenance Cleanup Tasks, check to make certain the file extension entered is bak and not .bak.
Save your change and then test it.
It is normal to put a “.” then the file type in most search type functions, but the “.” in MSSQL will make it so nothing is deleted.