Adjusting entries are posted at the year end. The trial balance is the first state and when the adjusting entries are posted, the result is called the extended trial balance.
The adjusting entries that are posted at the year end relate to depreciation, amortization, accruals, prepayments, deferred income, accrued income, deferred tax and the tax expense. There can be more than adjusting entries mentioned above but these are the most common ones.