Tax Accounting Deep Dive — Corporate Tax, Individual Income Tax, and Sales Tax

Corporate Income Tax — Book-Tax Differences

$$\begin{aligned} &\text{Taxable income calculation}: \\ &\text{Book income} (\text{GAAP net income}) \\ &\pm \text{Book-tax adjustments} (M-\frac{1}{\text{Schedule}} M-3) \\ &= \text{Taxable income} (\text{Form} 1120, \text{Line} 28) \\ &\text{Permanent differences} (\text{no deferred tax}): \\ &\text{Items included in book income but never in taxable income} \\ &(\text{or vice versa}), \text{AND vice versa} — \text{never reverse} \\ &\text{Examples}: \\ &+ \text{Tax-exempt interest on municipal bonds} (\text{book income}; \text{not taxable}) \\ &+ \text{Dividends Received Deduction} (\text{taxable income deduction}; \\ &\text{reduces book tax expense but is} a \text{permanent benefit}) \\ &− \text{Meals and entertainment} (50\% \text{disallowed permanently under TCJA}) \\ &− \text{Life insurance proceeds on key-person policies} (\text{book income}; \text{tax-exempt}) \\ &− \text{Fines and penalties} (\text{book expense}; \text{not tax-deductible}) \\ &\text{Temporary differences} (\text{create deferred taxes}; \text{reverse over time}): \\ &\text{Examples of taxable temporary differences} ( \to DTL): \\ &\text{Accelerated MACRS depreciation} > \text{straight-line book depreciation} \\ &\text{Installment sales recognized ratably for book}; \text{deferred for tax} \\ &\text{Examples of deductible temporary differences} ( \to DTA): \\ &\text{Warranty expense accrued for book}; \text{deductible when paid for tax} \\ &\text{Allowance for credit losses} (\text{CECL for book}; \text{specific charge-off for tax}) \\ &\text{Net operating loss} (NOL) \text{carryforward}: §172 \text{deduction} \end{aligned}$$

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Individual Income Tax Structure

$$\begin{aligned} &\text{Federal Individual Income Tax} (\text{Form} 1040): \\ &\text{Gross Income} (§61 — \text{all income from whatever source}) \\ &− \text{Above-the-line deductions} (\text{adjustments to income}): \\ &\text{Student loan interest}, \text{HSA contributions}, \\ &\text{self-employment tax deduction}, \text{alimony} (\text{pre}-2019) \\ &= \text{Adjusted Gross Income} (AGI) \\ &− \text{Greater of Standard Deduction or Itemized Deductions}: \\ &\text{Standard deduction} (2024): \$14,600 \text{single} / \$29,200 MFJ \\ &\text{Itemized} (\text{Schedule} A): \text{SALT cap} \$10,000; \text{mortgage interest}; \\ &\text{charitable contributions}; \text{medical expenses} >7.5\% \text{of AGI} \\ &− \text{QBI Deduction} (§199A): \text{up to} 20\% \text{of qualified business income} \\ &\text{for pass-through owners} (\frac{\text{subject to income limits}}{W}-2 \text{wage tests}) \\ &= \text{Taxable Income} \\ &\text{Tax Rates} (2024 \text{Married Filing Jointly}): \\ &10\%: \$0 – \$23,200 \\ &12\%: \$23,201 – \$94,300 \\ &22\%: \$94,301 – \$201,050 \\ &24\%: \$201,051 – \$383,900 \\ &32\%: \$383,901 – \$487,450 \\ &35\%: \$487,451 – \$731,200 \\ &37\%: \text{over} \$731,200 \\ &\text{Preferential rates} (\frac{\text{Net Long-Term Capital Gains}}{\text{Qualified Dividends}}): \\ &0\% / 15\% / 20\% \text{depending on taxable income bracket} \\ &\text{Retirement income}: \\ &\frac{\text{Traditional IRA}}{401}(k): \text{pretax contributions}; \text{ordinary income on distributions} \\ &\frac{\text{Roth IRA}}{\text{Roth}} 401(k): \text{after-tax contributions}; \text{qualified distributions tax-free} \end{aligned}$$

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US Sales and Use Tax

Sales Tax

• Consumption tax; imposed at the state and local level (no federal sales tax in the US)

Taxable events

• Sale of tangible personal property
• Selected services (varies by state)
• Digital goods (increasingly taxable; varies by state)

Tax rates

• State rates: 0% (Oregon, Montana, New Hampshire, Delaware, Alaska) to 7.25% (California)
• Combined state + local: up to ~10%+ in some jurisdictions

Exemptions (common across states)

• Groceries and prescription drugs
• Resale purchases (for resale → buyer provides resale certificate)
• Manufacturing equipment (in many states)
• Services (B2B services often exempt; varies widely)

Economic Nexus (South Dakota v. Wayfair, 2018)

• Remote sellers with >$100,000 in sales OR >200 transactions in a state must collect and remit that state’s sales tax
• Prior physical presence standard (Quill) overruled

Reporting

• Sellers file periodic sales tax returns (monthly/quarterly/annual) based on state requirements
• Streamlined Sales and Use Tax Agreement (SSUTA):
  • voluntary simplification framework adopted by 24 states

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Key Concept Cards

Book-Tax Differences: Permanent vs. Temporary ★★★★★ : Permanent differences (fines, tax-exempt income) → never reverse → no deferred tax. Temporary differences → reverse → create DTA or DTL. Memory hook: permanent = no deferred tax; temporary = deferred tax

Sales Tax = No Federal Component ★★★★★ : The US has NO federal sales tax. Sales and use tax is exclusively state/local. Post-Wayfair: economic nexus means remote sellers must collect where they have significant sales activity. Memory hook: sales tax = state only; Wayfair = economic nexus

Individual Income Tax Rate Range ★★★★☆ : Seven brackets, 10%–37% marginal rates (ordinary income). Long-term capital gains taxed at preferential 0%/15%/20% rates. Memory hook: 7 brackets, 10–37%; LTCG = 0/15/20

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Practice Quiz

Q. A corporation pays a $50,000 fine to the EPA. How is this treated for tax purposes?

Fines and penalties paid to a government agency are permanently non-deductible under IRC §162(f). The $50,000 book expense is added back on Schedule M-1 / M-3, increasing taxable income relative to book income. Because this is a permanent difference, there is no deferred tax consequence — only a higher current tax expense than what the GAAP effective tax rate would otherwise reflect.

Q. What is the difference between sales tax zero-rating and a sales tax exemption?

In the US sales tax context: an exemption means no tax is collected on the transaction, and the seller incurs no sales tax (e.g., resale, certain groceries). A concept analogous to VAT “zero-rating” does not technically exist in US sales tax, but the comparable concept is “exempt with credit” — effectively, in states with a manufacturing exemption, the seller pays no tax on inputs and does not charge tax on exempt sales, but also does not receive a direct refund mechanism (unlike VAT). Note: This contrasts with the VAT zero-rate / exemption distinction (IFRS context) covered in international tax courses.