Breakdown of sajangnimi da-eum dare gyeyak naeyongeul dasi hwaginhajago haesseo.
Questions & Answers about sajangnimi da-eum dare gyeyak naeyongeul dasi hwaginhajago haesseo.
-자고 했어 is the indirect-quotation form for a suggestion.
- 확인하자 = let's check / let's confirm
- 확인하자고 했어 = (someone) said we should check / suggested checking
So the boss is not simply stating a fact. He is proposing that they check the contract details again next month.
They are similar, but the nuance is different:
확인하자고 했어 = said, “let’s confirm/check”
→ a suggestion including the speaker/listener group
→ like Let’s check it again확인하라고 했어 = told (someone) to confirm/check
→ more like an instruction or command
→ like He told us to check it again
So in your sentence, the boss is presented as suggesting a joint action, not just ordering someone else to do it.