How to Check Your First Amazon FBA Deal (UK, With Real Numbers)

The first skill is not finding products — it is judging one correctly. One real UK deal worked end to end, including the three fees that catch beginners out.

Almost every guide to starting Amazon FBA in the UK begins by telling you to pick a product. That is the wrong first step, and it is why so many people lose their first few hundred pounds. The first skill is not finding products — it is being able to look at a product and say, correctly, whether it is worth buying.

Get that right and sourcing is a numbers game you can win. Get it wrong and better sourcing just helps you lose money faster.

This guide walks one real deal end to end, in UK numbers, including the three fees that catch beginners out. By the end you will be able to check a deal yourself.

The three words you have to know first

You cannot follow anything else until these are second nature. There are only three.

• ASIN — Amazon's unique code for a product, like B08N5WRWNW. Every listing has one. It is in the URL and on the product page. When someone says “send me the ASIN”, they mean this.
• BSR — Best Sellers Rank. How well a product sells in its category, where 1 is the best seller. BSR is meaningless without its category. A BSR of 50,000 in Beauty is a product selling several times a day. The same number in a tiny niche category might be a few sales a year.
• Buy Box — the “Add to Basket” button. When several sellers offer the same product, only one holds the Buy Box at a time, and they get the overwhelming majority of the sales. If you are not in the Buy Box you are largely invisible, no matter what your listing says.

What a deal actually looks like

Here is a real shape of deal, with the maths written out. Assume you are not VAT registered — that is where most people start, and it is the harsher of the two cases.

The product

• You find it in a UK retailer's clearance for £8.00 including VAT
• It sells on Amazon UK for £24.00 including VAT
• BSR around 40,000 in Beauty — sells steadily, not a rocket
• Four other sellers, none of them Amazon itself

£8 in, £24 out. It looks like £16 of profit. It is not. Here is where the £16 goes.

The fees

• Referral fee — £3.60. Amazon takes a percentage of the sale, commonly 15%. Critically, it is charged on the VAT-inclusive price. 15% of £24 is £3.60, not 15% of the £20 ex-VAT figure. This single detail is the most common error in beginner spreadsheets.
• FBA fee — around £2.70. Picking, packing and posting it. Driven by size and weight, so a bulky low-value item can be a terrible deal even at a good margin percentage.
• Your costs — around £0.50. Prep and the shipping to get it into Amazon. Most UK sellers budget 20-50p a unit. It is small, and leaving it out is how a marginal deal looks fine.

What you actually make

£24.00 sale − £3.60 referral − £2.70 FBA − £0.50 costs − £8.00 you paid = £9.20 net profit per unit. On £8 spent, that is roughly 115% ROI.

That is a strong deal. Most are not. The point of writing it out is that you now know which numbers to look for, and that “buy for £8, sell for £24” on its own tells you almost nothing.

The floor: 30% ROI and £3 a unit

Most UK sellers will not buy below roughly 30% ROI and £3 net profit per unit. Those two numbers together, not either alone.

The reason is not greed, it is survival. Thin deals have no room for the things that actually happen: a competitor undercuts you the week your stock lands, Amazon adjusts a fee, a customer returns one, or the product sells slower than you thought and starts accruing storage. On a 50% ROI deal all of those are annoying. On a 12% deal any one of them turns the buy into a loss.

ROI percentage alone is also misleading at small numbers. 60% ROI on a £2 item is £1.20 a unit — you would need to sell hundreds to make it worth the handling. That is why the £3 floor sits alongside the percentage.

The four things that kill beginner deals

1. Amazon is selling it themselves. Check the Buy Box. If Amazon is on the listing, you will rarely hold it. Most experienced sellers skip these entirely.
2. You are not allowed to sell it. Many brands and categories are “gated” — you need approval, usually with a proper wholesale invoice. Always check whether you can list a product before you buy it, not after. A garage full of stock you cannot list is the most common expensive beginner mistake.
3. The price you saw was a spike. One high price does not mean the product sells at that price. Look at the history. If it normally sits at £15 and briefly touched £24, your maths is wrong.
4. Too many sellers already. A dozen sellers on a listing means the price is heading down. You are all competing for one Buy Box, and the usual way people compete is by undercutting.

Your first week

In order. Do not skip ahead — the point of week one is judgement, not a sale.

1. Days 1-2: set your numbers. Decide your minimum ROI and minimum profit per unit. Write them down. These are the rules you check deals against, and having them in advance stops you talking yourself into a bad buy.
2. Days 2-4: check ten deals, buy none. Run ten real products through the full maths above. Most will fail. That is the correct outcome and it is the whole exercise — you are calibrating, not shopping.
3. Day 5: check you can actually sell it. Take the best one or two and confirm you are not gated on the brand or category.
4. Days 6-7: buy small. One product, 5-10 units, money you can afford to lose. The goal is to go through the whole cycle once — buy, prep, ship, list, sell — not to make money.

What to do next

Once you can look at a product and confidently say yes or no, the constraint becomes how many products you can check. That is when tools start earning their keep: a scanner that checks a whole supplier list at once, and a feed of deals someone has already run the maths on.

Until then, checking ten deals by hand is the most valuable week you will spend. Nothing you buy later works without it.