On the Stock Items screen you can link sales of a specific item to an individual ledger account by selecting it in the field Alternative Sales Ledger A/c. Otherwise all sales of the item will be recorded in the ledger account specified in the field Sales A/c on the File menu, Configure item, Global tab.
The calculation of Net Income for a business is only indirectly related to the volume of sales because it must also take account of overhead expenses.
I believe the best way to make provision for income tax in the ledger is to do it at a fixed % based on the sales a/c. This % could be an estimate based on the previous years business experience.
LedgerPlus will not allow customers or their accounts to be deleted.
If you really want to be rid of them do this.
Create a customer with the name "Unused Accounts."
Customer Accounts - delete all entries in the account. Then edit the account and change the customer to "Unused Accounts."
Customers - edit the customer and change the name to "Deleted Customer." Then blank out all the other fields.