Depreciation: Tax vs. GAAP
The biggest driver of book-tax differences — and the source of most deferred tax liabilities.
Educational only — not tax advice. MACRS rates and Section 179 limits are simplified for learning. Consult a CPA for asset-specific elections.
Why This Matters
Depreciation is the allocation of an asset's cost over its useful life. Under GAAP, that allocation follows economic reality. Under the tax code (MACRS), it follows Congressional policy — front-loaded, accelerated, designed to incentivize business investment.
ABC Coffee Shop — $100,000 espresso machine
For books: $10,000/year for 10 years. For taxes: $20,000 in Year 1, $32,000 in Year 2… or potentially $100,000 in Year 1 with Section 179. Same asset. Same cost. Completely different income statements.
This is the #1 source of deferred tax liabilities on most corporate balance sheets.
GAAP Depreciation
GAAP depreciation allocates cost over estimated useful life — the matching principle in action.
METHOD 1: STRAIGHT-LINE (most common)
Annual = (Cost − Salvage) / Useful Life
ABC espresso machine:
Cost $100,000 − Salvage $10,000 / 10 years = $9,000/year
METHOD 2: DOUBLE DECLINING BALANCE
DDB Rate = 2 × (1 / Useful Life). Switch to SL when SL > DDB.
METHOD 3: UNITS OF PRODUCTION
Depreciation per unit × Units produced. Useful for mining, printing presses.
Tax Depreciation: MACRS
The Modified Accelerated Cost Recovery System (MACRS) is required by the IRS. No management judgment — look up the property class, apply prescribed rates.
MACRS 5-YEAR ($100K asset):
Yr 1: 20% = $20,000
Yr 2: 32% = $32,000
Yr 3: 19.2% = $19,200
Yr 4–5: 11.52% each
Yr 6: 5.76% = $5,760
52% in first 2 years!
MACRS 7-YEAR ($100K asset):
Yr 1: 14.29% = $14,290
Yr 2: 24.49% = $24,490
Yr 3: 17.49% = $17,490
…through Year 8 (4.46%)
Office furniture, fixtures, most equipment
Half-year convention: A 5-year property class spans 6 tax years — half a year in Year 1 and half in Year 6.
Section 179 & Bonus Depreciation
SECTION 179 (2025):
→ Full cost deduction in Year 1 (limit: $1,250,000)
→ Cannot create a loss; business use > 50%
BONUS DEPRECIATION:
→ 100% immediate expensing on qualified property
→ No dollar limit; can create NOL carryforward
BOOK IMPACT: ZERO.
GAAP still uses straight-line. Sec 179/bonus are purely tax elections.
Books: $9,000 Yr 1 | Tax: $100,000 Yr 1 → $91,000 difference → massive DTL
Side-by-Side Depreciation Comparer
Compare GAAP straight-line depreciation against MACRS or Section 179. Watch book vs. tax basis, the cumulative temporary difference, and the deferred tax liability over each year.
| Year | GAAP Depr | Tax Depr | Book Basis | Tax Basis | Cumul. Diff | DTL @ 21% |
|---|---|---|---|---|---|---|
| 1 | $10,000 | $20,000 | $90,000 | $80,000 | $10,000 | $2,100 |
| 2 | $10,000 | $32,000 | $80,000 | $48,000 | $32,000 | $6,720 |
| 3 | $10,000 | $19,200 | $70,000 | $28,800 | $41,200 | $8,652 |
| 4 | $10,000 | $11,520 | $60,000 | $17,280 | $42,720 | $8,971 |
| 5 | $10,000 | $11,520 | $50,000 | $5,760 | $44,240 | $9,290 |
| 6 | $10,000 | $5,760 | $40,000 | $0 | $40,000 | $8,400 |
| 7 | $10,000 | $0 | $30,000 | $0 | $30,000 | $6,300 |
| 8 | $10,000 | $0 | $20,000 | $0 | $20,000 | $4,200 |
| 9 | $10,000 | $0 | $10,000 | $0 | $10,000 | $2,100 |
| 10 | $10,000 | $0 | $0 | $0 | $0 | $0 |
GAAP Annual
$10,000/yr
Peak DTL
$9,290
Final Year DTL
$0
Should reach $0 when fully depreciated
Units of Production (GAAP)
When asset wear is tied to usage rather than time, GAAP allows units-of-production depreciation:
Depreciation per unit = (Cost − Salvage) / Total estimated units
Annual depreciation = Depreciation per unit × Units produced
Useful for mining equipment, printing presses, and vehicles with predictable mileage. Tax still uses MACRS regardless — creating another book-tax timing difference.
MACRS 7-Year Property
Office furniture, fixtures, agricultural machinery ($100K asset):
Year Rate Depreciation 1 14.29% $14,290 2 24.49% $24,490 3 17.49% $17,490 4 12.49% $12,490 5 8.93% $8,930 6 8.92% $8,920 7 8.93% $8,930 8 4.46% $4,460 Total 100.00% $100,000
7-year property spans 8 tax years due to the half-year convention — same principle as 5-year property.
Real Property: Straight-Line MACRS
Not all MACRS is accelerated. Real property uses straight-line MACRS with mid-month convention:
27.5-YEAR RESIDENTIAL RENTAL:
Annual rate: ~3.636% per year
Used for: residential rental buildings
Mid-month convention applies
39-YEAR COMMERCIAL REAL PROPERTY:
Annual rate: ~2.564% per year
Used for: office, retail, warehouse buildings
No Section 179 or bonus on real property
Real property MACRS is much closer to GAAP straight-line, so book-tax differences on buildings are smaller and longer-lived than on equipment — but they still exist due to different useful lives and conventions.
GAAP Double Declining Balance
$100K machine — DDB Rate = 2 × (1/10) = 20%
Year Beginning BV Rate Depreciation Ending BV 1 $100,000 20% $20,000 $80,000 2 $80,000 20% $16,000 $64,000 3 $64,000 20% $12,800 $51,200 4 $51,200 20% $10,240 $40,960 ... Switch to straight-line when SL > DDB
DDB is more common in manufacturing. Even GAAP DDB is still typically slower than MACRS 5-year in the early years — the book-tax gap persists.
Scenario A: GAAP SL vs. MACRS 5-Year
$100K asset — GAAP 10-yr SL ($10K/yr) vs. MACRS 5-year
Year GAAP Depr MACRS Depr Cumul. Diff DTL @ 21% 1 $10,000 $20,000 ($10,000) $2,100 2 $10,000 $32,000 ($32,000) $6,720 3 $10,000 $19,200 ($41,200) $8,652 4 $10,000 $11,520 ($42,720) $8,971 5 $10,000 $11,520 ($44,240) $9,290 6 $10,000 $5,760 ($40,000) $8,400 7–9 $10,000 $0 declining… reversing 10 $10,000 $0 $0 $0
At Year 10, DTL fully reverses to $0. That's what "temporary" means.
Scenario B: GAAP SL vs. Section 179
GAAP 10-yr SL vs. Section 179 (full immediate deduction)
Year GAAP Depr Tax Depr Difference DTL @ 21% 1 $10,000 $100,000 ($90,000) $18,900 ← DTL peaks 2 $10,000 $0 $10,000 $16,800 ← begins reversing 3 $10,000 $0 $10,000 $14,700 4 $10,000 $0 $10,000 $12,600 5 $10,000 $0 $10,000 $10,500 6 $10,000 $0 $10,000 $8,400 7 $10,000 $0 $10,000 $6,300 8 $10,000 $0 $10,000 $4,200 9 $10,000 $0 $10,000 $2,100 10 $10,000 $0 $10,000 $0 Year 1: $18,900 DTL on balance sheet. Years 2–10: DTL decreases $2,100/year. Year 10: DTL = $0.
Section 179 and bonus depreciation maximize Year 1 cash tax savings but create the largest possible DTL on the balance sheet — a trade-off every business owner should understand before making the election.
Book Value vs. Tax Basis
ASC 740 focuses on the balance sheet — the difference between book carrying value and tax basis.
After Year 1 (MACRS 5-year, $100K):
Book carrying value: $100,000 − $10,000 = $90,000
Tax basis: $100,000 − $20,000 = $80,000
Difference: $10,000 (book > tax basis)
DTL = $10,000 × 21% = $2,100
Future taxable income will EXCEED book income when MACRS deductions run out → DTL.
Financial Statement Flow
YEAR 1 — ABC (simplified):
Pre-tax book income: $100,000
Current tax (payable): $18,690
Deferred tax (DTL increase): + $2,100
Total income tax expense: $20,790
Net income: $79,210
Balance sheet: Deferred tax liability $2,100
Tax expense ($20,790) ≠ taxes payable ($18,690). The $2,100 = DTL.
Depreciation Recapture (IRC §1245)
When you sell for more than tax basis:
ABC: $100K machine, $100K Sec 179 → tax basis $0.
Sells 3 years later for $40,000.
GAAP: $40K − $70K book value = ($30K) loss
Tax: $40K − $0 basis = $40K ordinary gain (§1245 recapture)
Section 179 creates $0 tax basis → maximum recapture exposure on any future sale.
Decision Framework
Use Sec 179 / Bonus when:
- ✓ High current income to offset
- ✓ Expect lower future income
- ✓ Asset unlikely to be sold early
- ✓ Cash flow benefit is valuable now
Use regular MACRS when:
- ✓ Expect growing income (future deductions more valuable)
- ✓ Presenting to lenders (stable book income)
- ✓ Asset may be sold soon (minimize recapture)
- ✓ Spread tax benefit over multiple years
Common Mistakes
Mistake 1: Assuming GAAP and tax depreciation must match
They never do by design. MACRS is required for tax; GAAP allows method choice. The difference is expected and legitimate.
Mistake 2: Forgetting Section 179 doesn't change the books
A 100% tax deduction in Year 1 with $0 book impact is the classic source of a large DTL. Lenders and investors see book income; the IRS sees tax income.
Mistake 3: Ignoring depreciation recapture on sale
Accelerated tax depreciation creates low or zero tax basis. Selling the asset triggers ordinary income recapture under IRC §1245 — often far more tax than the GAAP gain/loss suggests.
Mistake 4: Using GAAP useful life for MACRS
MACRS class life is determined by IRS property class, not management's estimate. A 10-year GAAP life doesn't mean 10-year MACRS.
Mistake 5: Not modeling the DTL reversal
The DTL created in Year 1 reverses over the asset's life. Financial models that ignore this overstate future cash tax savings.
Connecting to ASC 740
Every dollar of depreciation timing difference flows through to the balance sheet as a deferred tax liability. The next module — Deferred Tax Assets & Liabilities — shows how all temporary differences (not just depreciation) are measured, recorded, and presented.
The chain: Book-tax difference (this module) → Temporary difference identified → DTL = (book basis − tax basis) × enacted rate → Recorded on balance sheet under ASC 740 → Reverses as depreciation schedules converge.
Related Topic
Depreciation Methods (GAAP)
Straight-line, double declining balance, and units of production — the book side of the comparison.
Key Takeaway
GAAP depreciation (typically straight-line) and tax depreciation (MACRS or Section 179/bonus) create the largest single source of book-tax differences. MACRS front-loads deductions — 52% of a 5-year asset in the first two years vs. ~20% under GAAP straight-line. This creates a DTL in early years that reverses later. Under ASC 740, DTL = (book carrying value − tax basis) × enacted tax rate.
Test Your Understanding
Question 1: ABC buys $50,000 equipment. GAAP: 5-year SL, no salvage. Tax: MACRS 5-year. After Year 1, book value = $40,000, tax basis = $40,000. Deferred tax liability exists of:
Question 2: ABC elects Section 179 on a $60,000 espresso machine. GAAP uses 10-year SL, no salvage. After Year 1, deferred tax liability is approximately:
Question 3: Under MACRS 5-year property, what percentage of the asset's cost is deducted in the first two years?
Ready to Practice?
Model MACRS vs. straight-line depreciation in the Practice Lab — trace book basis, tax basis, and deferred tax liabilities year by year.
Try the Practice Lab