can take (something) to the bank
Can believe a particular statement or piece of information because it is definitely true (at least according to the speaker). I heard from a very reliable source that this company is about to close—you can take it to the bank.
can take it to the bank
Fig. able to depend on the truthfulness of my statement: it is not counterfeit or bogus; to be able to bank on something. Believe me. What I am telling you is the truth. You can take it to the bank. This information is as good as gold. You can take it to the bank.