If you need to use an opening balance to setup new accounting for an existing business (like a credit card in use, but they only want transactions entered for the current year), do you have to create a journal entry later to clear out the "opening balance" category? I thought Opening balance should always be zero, but how do I get those amounts out of there?

So a credit card with transactions in December & January, statement date is Jan. 10; I need to reconcile it without bringing in all the transactions from December. So do I add those and create an "opening balance" with the sum? Then will it reconcile properly when I add all the January transactions?

Then, won't the balance sheet show that sum in the Opening Balance Equity account? How do I make a journal entry to remove that?

You just bring all the opening balances in in a journal detailing them. Since what has happened previously is not your concern and what you are dealing with is net equity