These are generated during the writing up and writing down of assets in a transaction, including both tangible and intangible assets.
A deferred tax asset is created by an asset write-down, and a deferred tax liability is created by an asset write-up.
Due to the frequent differences between an asset's "fair market value" and its book value, which appears on the balance sheet, you must write down and write up the asset.
A write-up of asset results in a deferred tax obligation since the new item will have a larger depreciation expense, which means you will pay less in taxes initially but will eventually have to pay them back, leading to the liability.
The inverse is true for an asset write-down and a deferred tax asset.