How does accelerated depreciation create a tax shield, and why is the present value of tax savings higher than with straight-line?

You're right that total depreciation expense over the asset's entire life is the same under any method. The advantage of accelerated depreciation comes from the time value of money — higher depreciation deductions in early years push more tax savings to the present, where they have greater value.

Example:

Ridgemont Logistics purchases a delivery truck for $200,000 on January 1, 2026. Useful life = 5 years, salvage =$0. Tax rate = 30%. Cost of capital = 8%.

Straight-Line Depreciation:

Annual depreciation = $200,000 / 5 =$40,000 each year

Annual tax shield = $40,000 x 30$12,000 each year

Double-Declining Balance (DDB):

Year	BV Start	DDB Rate (40%)	Depreciation	Tax Shield (30%)
1	$200,000	40%	$80,000	$24,000
2	$120,000	40%	$48,000	$14,400
3	$72,000	40%	$28,800	$8,640
4	$43,200	40%	$25,920*	$7,776
5	$17,280	—	$17,280	$5,184
Total			$200,000	$60,000

*Switched to SL in Year 4 to fully depreciate.

Total tax shield under both methods = $60,000 (identical).

But the present value differs:

PV of SL tax shields = $12,000 x PVIFA(8$12,000 x 3.9927 = $47,913

PV of DDB tax shields = $24,000/1.08 +$14,400/1.08^2 + $8,640/1.08^3 +$7,776/1.08^4 + $5,184/1.08^5

= $22,222 +$12,346 + $6,859 +$5,715 + $3,528 = **$50,670**

PV advantage of DDB = $50,670 -$47,913 = $2,757

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Why this matters:

A dollar of tax savings today is worth more than a dollar of tax savings in five years. By front-loading depreciation, the company effectively receives an interest-free loan from the government — paying less tax now and more tax later.

Analyst adjustments: When comparing companies using different depreciation methods, analysts should be aware that accelerated depreciation reduces early-year earnings and creates larger deferred tax liabilities (since book depreciation exceeds tax depreciation under SL for financial reporting while using accelerated for tax). This temporary difference reverses in later years.

Exam tip: CFA Level I questions on this topic often ask you to compare after-tax cash flows under different methods or to identify which method maximizes the present value of tax savings. Always remember: total savings are the same, but timing makes accelerated methods more valuable.

For more depreciation and tax shield analysis, explore our CFA Level I FRA course.