Here is an illustrative founder question: "We import our supplements from China. Our agent declares our capsules at 12% duty, but another founder swears they pay 0% on what sounds like the same product. Who is right, and how do we know our code is the right one?" Here is the direct answer: you are probably both right, and that is exactly the problem. Duty is set by the commodity code on your declaration, not by what you call the product. The same sounding supplement can sit in codes with 0%, 8% or 12% duty depending on what is in it and how it is presented. Get the code wrong one way and you overpay for years. Get it wrong the other way and HMRC comes back for the difference.
I spend my days on import costs and margin for social commerce brands, and duty is one of the quietest expensive lines on the page. Every worked example below is a synthetic illustrative example you can rerun with your own shipments.
Here's the Short Version
- Duty is decided by the commodity code, a 10 digit number on the declaration, not by the invoice description. Same supplement, different code, different bill
- Finished supplements usually sit in chapter 21 food preparation codes. On the live UK tariff on 16 September 2026, 2106 90 98 69 showed 8% third country duty and 2106 90 92 85 showed 12%
- Vitamins as substances usually sit in chapter 29 (2936 90 00 00 showed 0%) and preparations put up as medicaments in chapter 30 (3004 50 00 00 showed 0%). That is how someone legitimately pays nothing on a product that sounds like yours
- On an illustrative £24,690 customs value: 8% duty is £1,975.20, 12% is £2,962.80, 0% is nothing. Across 4 shipments, 12% versus 0% is £11,851.20
- The declaration is yours even when an agent files it. HMRC's due diligence guidance says you can be liable for misdeclarations made by you, or by anyone representing you
- You can get certainty first: an Advance Tariff Ruling is legally binding, generally valid for 3 years, and HMRC replies in 30 to 120 days
- Fix past mistakes in both directions: reclaim overpaid duty within 3 years, disclose underpaid duty before HMRC finds it first
How a Commodity Code Decides Your Duty
Every imported line needs a commodity code, a 10 digit number that sets the duty rate and decides which rules, licences and reliefs apply. On the UK Integrated Online Tariff the rate shows in a column called third country duty, which is the rate for countries without a preferential trade agreement. China has no preferential deal with the UK, so Chinese origin goods pay those standard rates.
Classification follows the goods as presented, not the marketing. The tariff's general rules of interpretation classify products by their objective characteristics: where something could fit two headings, the most specific description wins, and the essential character of the product decides the hard cases. A vitamin imported as bulk material for manufacturing, the same vitamin in finished capsules for consumers, and a preparation put up in measured doses for a therapeutic use are three different customs animals, even if all three say "vitamin" on the label.
Here is the part most founders miss. The code is your responsibility, even though someone else types it. HMRC's due diligence guidance is blunt: you are responsible for working out which rules apply and which duties may be payable, and if you do not take due care you can end up liable for extra duties and import VAT because of misdeclarations made by you, or by anyone representing you on your declarations. If your agent acts as your direct representative, the customs debt is yours, not theirs. The agent submits the entry; you carry the bill. So the code is not paperwork your forwarder quietly settles. It is a decision to sign off, in writing, before the goods move.
The Three Chapters Your Supplements Live In
Supplements do not have one home in the tariff. They have three, and the duty rates do not look alike. These are the exact rates we checked on the live tariff on 16 September 2026.
| Where the product sits | Code checked | Third country duty | What tends to fit |
|---|---|---|---|
| Chapter 21, food preparations | 2106 90 98 69 | 8% | Finished supplements sold as food, including the catch all line for other food preparations |
| Chapter 21, other food preparations line | 2106 90 92 85 | 12% | The line for products with no milkfats, sucrose, glucose or starch, or less than the threshold amounts |
| Chapter 29, vitamin substances | 2936 90 00 00 | 0% | Vitamins and provitamins as substances, including natural concentrates |
| Chapter 30, medicament preparations | 3004 50 00 00 | 0% | Preparations containing vitamins put up as medicaments |
Read the third column and the opening mystery disappears. Two founders with products that sound the same can pay different duty because in customs terms the products are not the same. The finished capsules most brands sell usually classify in chapter 21, and the two lines we checked carry 8% and 12%. The split turns on composition, including milk fats, sucrose, glucose and starch content, so similar looking capsules can land on different rates. Float up to the vitamin substance in chapter 29, or a medicament preparation in chapter 30, and the rate falls to zero. And watch the fine print: sibling codes inside chapter 21 carry their own rates, so the honest answer to "what code do supplements use" is that it depends on the exact product, its ingredients, form and presentation. An agent quoting a rate off the invoice description is a red flag.
One warning about the 0% lines, because this is where wishful classification lives. Chapter 29 is for the vitamin as a substance, typically bulk material or concentrate for manufacturing. Chapter 30 is for preparations in measured doses or retail form with a therapeutic use. A finished food supplement is a different animal, and a code from the wrong chapter quietly builds an underpayment. If your margin only works at 0%, treat that as information: the product may not fit the 0% code, and the missing duty is a cost you have not priced.
What the Duty Gap Looks Like in Real Money
Here is the illustrative example, built on the same shipment shape as our landed cost model. A supplement brand imports 10,000 bottles from China: supplier price £2.20 a bottle, sea freight £2,600, cargo insurance £90, so the customs value, the goods plus freight and insurance to the UK border, is £24,690. Figures are net of recoverable VAT; this is a synthetic example, not a client shipment.
| Duty scenario, illustrative example | Rate | Duty per shipment | Duty across 4 shipments |
|---|---|---|---|
| Chapter 29 or chapter 30 classification holds | 0% | £0 | £0 |
| Chapter 21 at the 8% line | 8% | £1,975.20 | £7,900.80 |
| Chapter 21 at the 12% line | 12% | £2,962.80 | £11,851.20 |
Now shrink it to a bottle, because that is where it reaches your pricing. On this shipment, 12% duty is about 29.6p a bottle and 8% duty is about 19.8p. Every percentage point of duty costs you about 2.5p a bottle, or £246.90 across the shipment. Across a year of 4 shipments, the gap between the 8% line and the 12% line is £3,950.40, and the gap between 12% and 0% is £11,851.20.
Scale that to the £1m revenue brand in our post on what a £1m TikTok Shop supplement brand really keeps. If a wrong code added 4 percentage points of duty across 40,000 bottles a year (12% instead of 8%), that is £3,950.40 gone from gross margin, about 0.4 of a percentage point of revenue. The 12% versus 0% version, where the product should have been in chapter 29 or 30, is £11,851.20, nearer 1.2 points. Both quietly reshape a P&L while everyone blames ad costs.
And notice the asymmetry, because it decides how you behave. An overpayment is money you can claim back within limits, but only if you notice it. An underpayment is a cost you still owe, off your books, so the margin you reported was flattered by exactly the amount you missed. Either way, the code decides, so treat the lookup as a real step in your costing, like freight. The full build of that model is in our post on the landed cost model for imported supplements.
How to Get Certainty: The Advance Tariff Ruling
You do not have to guess: HMRC's Advance Tariff Ruling service settles the question properly. You apply before the goods clear customs, because HMRC cannot decide retrospectively, and it can refuse applications once the goods are cleared or if you are not actually planning to import. You describe the product in detail, with its composition, presentation and the evidence HMRC asks for, photographs or samples included, and you can mark attachments as confidential.
HMRC replies in 30 to 120 days and gives you a legally binding decision: the correct commodity code, the start date of its validity, and a reference number that identifies your goods. The ruling is generally valid for 3 years, it is issued to you and is not transferable, and you declare the reference in Box 44 of your customs entry so the declaration and the decision line up. Change the formula or presentation and the description may no longer fit, so check before you assume the same code still applies.
Two practical moves. Plan the lead time: build the ruling into your launch calendar, because if it lands after your first shipment sails, it is too late. And use HMRC's published decisions as research: they appear with confidential detail removed, so you can see how HMRC classified near identical products. If your agent's code contradicts a published ruling, ask harder questions. Treat this as part of your compliance set up; we covered that budget in our post on how a 6 figure supplement brand should budget for compliance before launch.
When the Code Was Wrong: Reclaim or Disclose
Classification mistakes run in two directions, and both have a fix.
If you overpaid, claim it back. You can claim overpaid import duty and VAT back, and the time limit is 3 years. On Customs Declaration Service declarations, you claim with the online C285 service, and repayments go only to a UK bank account. One split to know: if you are VAT registered, overpaid import VAT is not claimed through that service, it goes through your VAT return instead. On our example numbers: a year of shipments declared at 12% when 0% was right is £11,851.20 of duty to claim, subject to HMRC accepting the evidence.
If you underpaid, disclose it. The route is a voluntary clearance amendment, the C2001 service, which tells HMRC about the underpayment and results in a charge, often called a C18, for the extra duty. If you used postponed VAT accounting, the import VAT side of the correction goes on your VAT return instead. We went deeper on the import VAT machinery in our post on VAT traps for UK supplement brands selling on TikTok Shop.
On penalties, the honest summary: customs has a civil penalty regime designed to encourage accurate declarations. For most contraventions, HMRC sends a warning letter before it charges a penalty for a first error of that type, and the maximum penalties are £2,500 per contravention for the more significant irregularities and £1,000 for others. The practical reading: correct mistakes early and in your own words, because HMRC finding them first is worse.
The Cash Flow Lever: Duty Deferment
One more piece of the machine, and it pays for itself once your duty bill has real size. A duty deferment account lets you make one payment a month by Direct Debit instead of paying at every consignment. On the Customs Declaration Service, a calendar month's deferred total is collected on the 16th of the following month, or the next working day after, giving between 2 and 6 weeks of credit, an average of 30 days.
To get one, you apply to HMRC, and you can apply for a guarantee waiver with the application instead of providing a financial guarantee from a bank. HMRC aims to complete applications within 30 working days when it has everything it needs. And if you use postponed VAT accounting, you do not need deferment for import VAT at all: it is declared and recovered on the same VAT return and never leaves your bank.
On the numbers above, 8% duty runs at £7,900.80 a year, roughly £658 a month. Deferment does not change the total, it changes when it leaves your account, and a month of lag is real breathing room when a container lands the same week as your VAT bill. Importing monthly, it is standard plumbing. Importing twice a year, focus on the code first.
What This Means in Your Accounts
Two accounting consequences follow, and both reach your margin, not just your compliance file.
First, duty is part of the cost of your stock, not an overhead. Import duties you cannot recover are part of the costs of purchase under FRS 102, so they sit in your inventory value and become cost of goods when the stock sells. That is what makes a wrong code so quiet: nothing in your bank statement screams, your gross margin just drifts from plan. We walked through the mechanism in the landed cost post linked above.
Second, corrections need booking properly, not just feeling dealt with. If duty was underpaid, the extra is a cost of that stock, or an expense if the stock has gone, and it belongs in the right period. If duty was overpaid, the recovery reverses the cost, and where the stock has sold, it flows back through your margin. Put these adjustments in front of your accountant as soon as you know about them, which is also when to decide whether a claim is worth making.
Last habit, and the cheapest one: keep the records. HMRC expects records for all traded goods you declare to be kept for 4 years, so your file should hold declarations, invoices, ruling references and postponed VAT statements. Then once a year, reconcile: add up the duty on your declarations and compare it with the duty in your accounts. A disagreement means a classification issue or an unclaimed refund, and both are cheaper to find yourself.
FAQ
What commodity code should a UK supplement brand use?
It depends on the product, not the label. Finished capsules, tablets and gummies usually classify in chapter 21 food preparation codes, where the rates we checked were 8% and 12% from China. Vitamins as substances usually sit in chapter 29 at 0%, and medicament preparations in chapter 30 at 0%. Because the gap is wide, check the exact code on the live tariff and get an Advance Tariff Ruling where the duty is material.
Can you reclaim customs duty if the commodity code was wrong?
Yes, if you overpaid. You can claim overpaid import duty and VAT back within 3 years of the declaration, using the online C285 service for CDS declarations; repayments go to a UK bank account. If you are VAT registered, overpaid import VAT goes through your VAT return instead.
What happens if you underpay import duty?
You have to put it right. A voluntary clearance amendment, the C2001 service, tells HMRC about the underpayment and results in a charge for the extra duty. Customs civil penalties can apply, with HMRC normally warning first for a first error of that type and maximum penalties of £2,500 per contravention for the more significant irregularities. If postponed VAT accounting was used, the import VAT correction goes on your VAT return instead.
The Bottom Line
Your supplier's quote starts the cost, but your commodity code starts the tax. Two founders can import "the same" supplement, pay 0% and 12%, and both be within the rules, because the code follows the product, not the pitch. On the numbers here, that difference was £11,851.20 across a year of shipments, more than most brands spend on things they would call major costs.
So build the discipline: check the code yourself, sign it off in writing, get a ruling when the duty is big, fix past errors in both directions, and keep the records that prove it. Do that and import duty becomes a number you control, not a tax you discover.
If you want us to review the duty position across your product range, including refunds sitting unclaimed, that is the kind of work we do regularly. We are specialist social commerce accountants working with UK ecommerce brands from £1m to £20m, and classification questions come across our desks every week. Book a call and we will work through the codes with you, line by line.