The profit and loss report (income statement) shows the changes in balances of your income and expense accounts. It runs from the previous consolidation. If there is no previous consolidation, the report runs from the date of the first transaction, and uses the opening balances if there are any.
You can change the start and end dates if you want to run the report over a different date range instead.
The end date defaults to the date of the next consolidation, and although you can view the profit and loss for a particular date range, you can only consolidate if the end date has passed, the start date is the beginning of the period, and the end date is the year end date defined in Business Settings.
Consolidation posts adjustment lines to all income and expense accounts to zero the balance for the start of the next financial year. The effect is that the overall profit is moved into your "profit and loss" account.
You can undo a previous consolidation in the profit and loss report using the Undo Last P/L button.
After consolidating the profit and loss, the adjustment lines are visible in the accounts. These lines can be viewed, but cannot be changed. The consolidation puts a lock on the transactions dated before the year end. These cannot be edited, and no new transactions can be added before this date.