you can bet your bottom dollar
US /ju kæn bɛt jʊər ˈbɑtəm ˈdɑlər/
UK /ju kæn bɛt jʊər ˈbɑtəm ˈdɑlər/
1.
to be absolutely certain about something; to be sure that something will happen
:
•
You can bet your bottom dollar that he'll be late.
•
If she says she'll do it, you can bet your bottom dollar it'll get done.