What you think, Finance and Banking departments best placed as separate departments or as a singal department?

It depends on the size and activity of the organization, in my opinion they have to be in one department

I am experiencing the situation at my new job that the operation are quiet large and company also involves in leasing from banks and LCs etc. But company is not a public limited and also do not have any plan for IPO in near future. But there are many departments working under finance/Tax/Accounts/Banking/etc. heads that i am confused and after many days still do not know what job is doing by what department.

For a big corporate entity banks may not provide for all the finances. The co may have to go to the public for an IPO or even take loan from other firms and even the govt. But for a small firm banking and fiance could be the same dept.