Tax Planning for E-Commerce Businesses: Amazon FBA, Multi-State Sales Tax Nexus, and Inventory Accounting

By Yarik Yarosh, CPA ·September 5, 2026 ·6 min read

Written by Yarik Yarosh, CPA (US & Canada) September 5, 2026 · FL CPA license AC61704 · CPA Ontario

E-commerce taxation has become dramatically more complex since the Supreme Court’s Wayfair decision eliminated the physical presence requirement for sales tax collection. Under the economic nexus framework, an online seller who ships products to customers in a state is required to collect and remit sales tax once they exceed that state’s threshold (most commonly $100,000 in sales or 200 transactions). For Amazon FBA sellers, the complexity multiplies: Amazon distributes inventory across its fulfillment network, which means a seller who sends inventory to a single Amazon warehouse may find their products stored in warehouses across 10-20 states, creating physical nexus in each one. While Amazon’s marketplace facilitator collection covers sales tax on marketplace sales in most states, sellers with their own websites (Shopify, WooCommerce) or who sell on platforms without facilitator collection must manage multi-state sales tax compliance themselves. For income tax purposes, the IRS treats e-commerce the same as any other retail business: IRC 471 requires businesses with inventory to account for COGS, and the gross profit (revenue minus COGS) is the starting point for taxable income.

✓Key takeaway

E-commerce sales tax nexus types:

Nexus Type	How It’s Created	States
Economic nexus (Wayfair)	$100K sales or 200 transactions in a state	45 states + DC (all with sales tax)
Physical nexus (inventory)	Inventory stored in a state (Amazon FBA warehouses)	All states with sales tax
Marketplace facilitator collection	Amazon, eBay, Etsy, Walmart collect on behalf of sellers	~45 states
Click-through nexus	Affiliate or referral links from in-state websites	~25 states
Cookie nexus	Placing cookies on devices of in-state customers	Limited states

Amazon FBA tax issues:

Issue	Details
Inventory nexus	FBA inventory in multiple states creates physical nexus in each
Marketplace facilitator	Amazon collects sales tax on marketplace sales in all applicable states
Own website sales	Seller must collect sales tax on Shopify/direct sales (not covered by Amazon’s collection)
FBA fees	Deductible business expense (not part of COGS)
Inventory valuation	Must track cost basis of inventory for COGS calculation
Returns and refunds	Reduce gross receipts (not a separate deduction)

Inventory accounting methods (IRC 471):

Method	Who Can Use	How It Works
FIFO (First-In, First-Out)	Any business	Oldest inventory costs are matched to revenue first
LIFO (Last-In, First-Out)	Any business (but must also use for financial reporting)	Newest inventory costs matched first (higher COGS in inflation)
Specific identification	Businesses with unique, identifiable items	Track actual cost of each unit sold
Simplified method (IRC 471(c))	Small businesses ($30M or less average receipts)	Treat inventory as non-incidental materials and supplies

How do e-commerce businesses minimize taxes?

Hypothetical example

Round numbers. An Amazon FBA seller has the following financials:

Item	Amount
Amazon marketplace sales	$800,000
Shopify direct sales	$200,000
Total revenue	$1,000,000
COGS (purchase price of goods)	($400,000)
Amazon FBA fees (fulfillment, storage, referral)	($250,000)
Shipping to Amazon warehouses	($30,000)
Advertising (Amazon PPC, Facebook ads)	($80,000)
Software and subscriptions	($10,000)
Home office	($3,000)
Other expenses	($27,000)
Net income	$200,000

COGS vs. business expenses (important distinction):

Item	COGS (IRC 471)	Business Expense (IRC 162)
Product purchase price	Yes	No
Inbound shipping (to warehouse)	Yes	No
Customs duties on imports	Yes	No
Amazon referral fees	No	Yes
Amazon FBA fulfillment fees	No	Yes
Amazon storage fees	No	Yes
Outbound shipping (to customer)	No	Yes (or included in sale price)
Returns/refunds	Reduces revenue	N/A
Packaging materials	Yes (if part of product)	Yes (if separate shipping materials)

Why it matters: COGS offsets revenue to produce gross profit. Business expenses are deducted below gross profit. Both reduce taxable income, but the classification affects how income is reported on the tax return and whether the simplified inventory method (IRC 471(c)) can be used.

Sales tax compliance:

Platform	Who Collects?	Seller’s Responsibility
Amazon (marketplace sales)	Amazon collects and remits	File returns in nexus states; Amazon handles collection
Shopify (direct sales)	Seller collects (or uses Shopify Tax)	Register in nexus states; configure Shopify to collect; file and remit
eBay (marketplace sales)	eBay collects and remits	File returns in nexus states
Own website (no platform)	Seller collects	Full responsibility for registration, collection, filing, remitting

Multi-state income tax filing:

Factor	Details
Physical nexus states (FBA inventory)	Must file income tax returns in each state
Economic nexus states	May need to file income tax returns (varies by state)
Apportionment	Income allocated to each state based on sales percentage (single-sales-factor in most states)

Example: $200,000 net income, sales in 30 states:

State	% of Total Sales	Apportioned Income	State Tax Rate	State Tax
California	15%	$30,000	8.84%	$2,652
New York	10%	$20,000	6.5%	$1,300
Texas	8%	$16,000	0% (no income tax)	$0
Florida	7%	$14,000	5.5% (corporate)	$770
All other states (60%)	60%	$120,000	Varies	~$5,000
Total state income tax				~$9,722

Entity structure for e-commerce:

Structure	Best For
Sole proprietorship	Startup phase; under $50K net income
Single-member LLC	Liability protection; under $50K net income
S-Corp	$75K+ net income (payroll tax savings)
C-Corp	Reinvesting all profits; seeking outside investment

S-Corp savings on $200,000 net income:

Structure	SE/Payroll Tax	Income Tax	Total
Sole proprietorship	$28,000	$74,000	$102,000
S-Corp ($80K salary)	$12,240	$74,000	$86,240
Savings			$15,760

Import duty and tariff deductions:

Item	Tax Treatment
Import duties and customs fees	Capitalized into inventory cost (part of COGS)
Customs broker fees	Deductible business expense
Anti-dumping duties	Capitalized into inventory cost
Section 301 tariffs (China)	Capitalized into inventory cost
Duty drawback (re-exported goods)	Refund reduces COGS

Illustrative numbers only, not a real client and not advice for your facts.

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Cite this page

Yarik Yarosh, CPA. "Tax Planning for E-Commerce Businesses: Amazon FBA, Multi-State Sales Tax Nexus, and Inventory Accounting." Blue Cloud CPA, September 5, 2026. https://bluecloudcpa.com/guides/small-business-tax-planning-ecommerce-amazon-fba-sales-tax-nexus

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.