Hi @Luisa Nogueira,

There are a couple of options, depending on which QuickBooks product you are using. For QuickBooks Online, if you want to keep the same QuickBooks company file, you will want to reconcile as much as possible and be sure to Close your books. You can create a journal entry for each account as a closing balance dated December 31st, 2020, and mark them reconciled. That way you will start recording in January with the opening balances matching December's closing balances. 

Or, 

You can get a new subscription:

• Export Accounts List and Import to the new account
• Enter the Opening Balance of each account.
• Mark all Opening Balances as reconciled.

Once you have exported all the information, you can close the original account. You will have access to all reports and lists for 18 months.

If you have QuickBooks Desktop, let me know and I can give you similar options. 

Take care!