The tax that rises on its own: why your margin shrinks as your store grows
In Simples Nacional, your tax rate isn’t fixed: it follows your accumulated revenue from the past twelve months. A retail store that grows from R$ 500,000 to R$ 2 million sees its effective rate rise from about 6.7% to nearly 9.9%. That’s over three margin points gone from every product at once, with no change in price, cost, or marketplace fee.
No one warns you. The product stays the same, the supplier stays the same, and the store simply starts earning less per sale while selling more.
#Nominal rate and effective rate are not the same thing
This confusion is costly.
The nominal rate is the percentage you see in the annex table, by revenue range. The effective rate is what you actually pay. From the second range on, it’s lower than the nominal, because there’s a deduction; only in the first range, up to R$ 180,000, do both rates match.
Here’s the math: multiply your last twelve months’ revenue by the nominal rate for your range, subtract the deduction, and divide the result by the same twelve-month revenue.
A retail store with R$ 600,000 accumulated falls into a 9.5% nominal range with a R$ 13,860 deduction. The effective rate is 7.19%. If you use 9.5% in your margin spreadsheet, you’re underestimating profit. If you use 4%, because that was the rate when you opened the business, you’re overestimating.
#How the rate rises as you grow
See the same product from a retail store at four different stages:
| 12-month revenue | Effective rate | Tax on a R$ 100 sale |
|---|---|---|
| R$ 300.000 | 5,32% | R$ 5.32 |
| R$ 500,000 | 6,73% | R$ 6.73 |
| R$ 900,000 | 8,20% | R$ 8.20 |
| R$ 2,000,000 | 9,94% | R$ 9.94 |
On a R$ 100 sale with a 20% margin, going from R$ 500,000 to R$ 2 million in annual revenue takes R$ 3.21 from each sale. That’s 16% of the profit on that product, lost to your own success.
Check the current ranges and deductions with your accountant before using these numbers, because the table is set by law and changes by law.
In practice. A housewares store was growing fast and repriced its catalog in January using the effective rate for that month. By September, with much higher twelve-month revenue, the rate had climbed almost two points. The store had increased revenue by 40%, but profit grew much less than expected, even though nothing visible had changed.
#The mistake of calculating tax on the amount received
There’s another common pitfall, and it goes hand in hand with the first.
For tax purposes, your revenue is the sale value to the customer, before marketplace fees. If the customer paid R$ 100 and the marketplace sent you R$ 74, you’re taxed on R$ 100. Commission and shipping are your expenses, not a reduction in revenue.
If you calculate tax on the net amount received, you think you pay less than you do—and the gap is bigger on cheaper products, where the fee is a larger share of the price. I wrote about this effect in Shopee’s payout in another article.
#Different rates by product
Not every item has the same tax burden. Products with ICMS tax substitution, single-phase PIS and Cofins, and some specific segments have their own rules, which can greatly reduce the bite on certain SKUs.
If your store mixes categories, using a single rate for everything distorts your margin both ways: you think you earn little on lightly taxed items and a lot on fully taxed ones. Ask your accountant for a list of your SKUs with special treatment and enter the correct rate for each product, not an average for the whole store.
#Tax reform: what you can do today
The transition to the new IBS and CBS model is underway and will change how consumption tax is calculated in the coming years, even for those in Simples, who will have choices to make about regime and credits.
No one needs to reprice today because of a rule that’s still being rolled out. What you should do now is keep tax separate within each product’s margin, instead of diluted in a generic percentage. When the rule changes, you swap one number and see the effect. If you have tax built in “by estimate,” you’ll have to rebuild everything.
In Milewa, the rate is set per product and each order’s margin already comes with tax deducted. And if you want to test the effect of a different rate on a specific price, the profit calculator accepts that field directly.
#Frequently asked questions
Which Simples Nacional rate should I use to calculate margin in a marketplace?
The effective rate, never the nominal one for the range. The effective rate is calculated by multiplying your last 12 months’ revenue by the range’s rate, subtracting the deduction, and dividing everything again by the 12-month revenue. From the second range on, it’s lower than the nominal, and changes every month as your accumulated revenue grows.
Is tax charged on the amount the marketplace pays me?
No. For tax purposes, your revenue is the sale value to the customer, before marketplace fees. Commission and shipping are your expenses, not a reduction in revenue, so calculating tax on the net received underestimates what you owe.
Why does margin drop as the store grows, even selling the same products?
Because the effective Simples rate rises as your accumulated revenue over the last 12 months moves up a range. A retail store that goes from R$ 500,000 to R$ 2 million sees its effective rate rise from about 6.7% to nearly 9.9%, which takes more than three points off the margin of every product at once.
#Sources
Marketplace fees change. The numbers in this article are valid for the period mentioned — before setting your price, check the current table in your account.
Want to see these numbers with your own data?
Milewa pulls your orders from Mercado Livre and Shopee, applies commission, shipping, tax, ADS, and your cost, and shows the margin for each order and each SKU. You can start with the calculator and then connect your store.