Within the Settings tab you will find a tab for System Settings: from here you can select the default accounts for Retained Earnings and Tax:
Things to note regarding the retained earnings selection:
The current period earnings balance (all P&L account balances) will flow into this account in the next period
It must be an account that falls under a Equity or Reserve classification
If you change this account in any period, that change will be reflected in all prior periods also
Account designated for Tax on Sales / Expenses:
These selections indicate where tax amounts will be posted when you post any bank transactions with tax or use Sales or Expense batch entries.
It is possible to change the designated account here after entries are made, but this will change the tax account set in all of the existing entries in the current period as well. The change will flow through all of them - existing & future entries across all periods.
Default account for Total/Gross balances in Sales / Expense batches:
These selections indicate where the total/gross amounts will be posted when you use Sales or Expense batch entries.
It is possible to change the designated account here after entries are made, but this will not change the account set in the existing entries already made (you would have to change these individually). It will however, change for future batch entries by default.
Note: it is always possible to change the account for Total/Gross amounts within a sales/expense batch entry. It is only for taxes that the designated account should remain consistent across all entries in a period.
You can also set the number of days for the duplicate checker in this section