From ACT Wiki
Depreciation that is an allowable expense under applicable tax laws.
Tax depreciation generally gives the same total tax relief over time, as the total accounting depreciation charged on the same assets over their total life.
However, the phasing of the tax relief will often differ from the phasing of the accounting depreciation charges.
These timing differences are one source of deferred tax assets and liabilities.
2. US tax.
US tax relief for capital expenditure under the Modified Accelerated Cost Recovery System (MACRS).