What is straight-line depreciation?

Straight-line depreciation spreads the depreciable base (cost minus salvage value) evenly over the asset's useful life. Annual depreciation = (Cost − Salvage Value) / Useful Life. Simple and predictable. Used for: buildings (27.5 or 39 years for tax), office furniture, vehicles in some cases.

What is double declining balance depreciation?

Double declining balance (DDB) front-loads depreciation — more expense in early years, less in later years. Annual rate = 2 / Useful Life. Applied to book value (not original cost). Switches to straight-line when straight-line gives a higher deduction. Good for assets that lose value quickly (tech, vehicles).