5 Things Amazon Sellers Get Wrong About Their Own Profitability

5 Things Amazon Sellers Get Wrong About Their Own Profitability

Most Amazon sellers can tell you their revenue to the dollar. Ask them their actual net profit on a specific SKU and you get a pause, a shrug, or a number they pulled from a Seller Central dashboard that was never built to answer that question.

That gap is where the money hides. The most expensive Amazon seller profitability mistakes don't come from bad products or weak ads. They come from accounting that quietly lies to you — booking the wrong numbers in the wrong months and calling it a P&L.

Here are the five that do the most damage, and what the number is supposed to look like once it's right.

1. The Amazon seller profitability mistake hiding in your settlement deposit

Every two weeks Amazon drops money in your bank account. It feels like revenue. It gets booked as revenue. That's mistake number one, and it poisons everything downstream.

A settlement deposit is not sales. It's sales, minus referral fees, minus FBA fulfillment fees, minus advertising, minus refunds, plus reimbursements, minus a dozen smaller line items — all netted into one number. Book that deposit as "revenue" and you've just told your books that a $100,000 sales period was a $61,000 sales period, and you've buried roughly $39,000 of fees you can no longer see.

Under ASC 606, revenue is recognized when you transfer the product to the customer — at the gross sale price. The fees Amazon takes are expenses, recorded separately. Amazon settlement accounting done right means decomposing each settlement report into its parts: gross sales here, referral fees there, ad spend in its own line, refunds against revenue, reimbursements as their own category.

The short answer: the deposit is the leftover, not the top line. If your top line is the leftover, your gross margin is fiction.

2. Expensing inventory when you buy it instead of when you sell it

This is the one that makes a great quarter look like a disaster — and a disaster look great.

Say you spend $80,000 on a big inventory buy in March to prep for Q2. If you expense that $80,000 in March, March looks like a bloodbath. Then April and May, when you actually sell the goods, look wildly profitable because the cost of those sales has vanished. Your P&L is now a funhouse mirror.

Inventory is an asset on the balance sheet until it sells. The cost moves to cost of goods sold in the month the unit ships to a customer — that's the matching principle, and it's the entire point of ecommerce inventory accounting. IRC §471 governs how inventory is accounted for; under §471(c), qualifying small businesses (those under an inflation-adjusted gross receipts threshold, $25M when the rule was written and indexed upward since) can use simplified methods, but even the simplified method treats inventory as "used and consumed" when you provide it to the customer — not when you swipe the card with your supplier.

Get this wrong and you can't trust a single monthly profit number. Get it right and your margins stop swinging for no reason.

3. Burying every Amazon fee in one "Amazon fees" line

PPC, referral fees, FBA fulfillment, monthly storage, long-term storage, returns processing — sellers love to mash these into a single "Amazon fees" expense and move on. It's tidy. It's also useless.

These fees behave completely differently and they hit different products. Advertising is a marketing decision you control. FBA fulfillment scales with units sold. Long-term storage is a penalty for slow movers eating shelf space. When they're collapsed into one line, you can't see that SKU A is carrying the business while SKU B is quietly losing money on storage and ad spend every single month.

Here's the pattern: break fees out by type, then allocate them to products. The first time most sellers do this, they find one or two "bestsellers" that are net-negative once true PPC and storage costs land on them. That's not a rounding error — that's the difference between a product line you scale and one you kill.

4. Assuming marketplace facilitator tax means you owe nothing

By 2026, every U.S. state with a sales tax requires the marketplace — Amazon — to collect and remit sales tax on your behalf. A lot of sellers read that as "sales tax is handled, I'm done." Then a state notice shows up and the panic starts.

Marketplace facilitator laws shift collection, not your reporting obligations. Most states still require you to report your gross marketplace sales on a sales tax return even when Amazon remitted the tax. If you also sell off-Amazon — your own Shopify store, a trade show, wholesale — those channels are still yours to collect and file on. And marketplace sales often count toward your economic nexus thresholds, which can pull you into new states you didn't think you had to register in.

The thing nobody tells you: keep your sales tax permits current in states where you have nexus, even if Amazon is doing the collecting. A facilitator only covers transactions on its own platform. Everything else is on you, notice or no notice.

5. The Amazon seller profitability mistake in your returns and reimbursements

Returns and Amazon reimbursements are the last place margin goes to die quietly.

When a customer returns a product, that's a reversal of revenue and a corresponding move of inventory cost. When Amazon reimburses you for a lost or damaged unit, that's a separate event — closer to other income than to a sale. Sellers routinely net these together, or net them against fees, and the result is a gross margin number that's a guess instead of a measurement.

If returns aren't booked as contra-revenue and reimbursements aren't tracked on their own, you can't tell whether a high-return SKU is destroying your margin or whether Amazon owes you money it never paid. Both happen constantly. Both are recoverable — but only if the books are clean enough to show them.

Find an ecommerce CPA who reads settlement reports for a living

Every mistake on this list comes from one root cause: general accounting applied to a marketplace it wasn't built for. The fix is someone who works in Amazon settlement reports all day and knows exactly where the errors hide.

ECOM CPA works exclusively with ecommerce sellers — Amazon, Shopify, Walmart Marketplace, nothing else. That's the whole practice, which is why they catch the settlement and inventory-timing problems generalists miss. They focus on established ecommerce businesses, typically $500K in revenue and up.

If your P&L swings for no reason and you can't say what a single SKU actually nets, read ECOM CPA's verified reviews on Sam's List and book an intro call. Bring one recent settlement report. You'll learn more in that conversation than your dashboard has told you all year.