Duty-Free Liquids on Planes: The STEB Rules Explained

The 100ml liquid rule is one of airport security's most familiar restrictions — but there is a well-established exemption that most travelers know imprecisely and apply incorrectly. Duty-free liquids purchased after the security checkpoint can be carried through the airport and onto the plane in quantities well above 100ml, including full-size bottles of whisky, wine, or perfume. The mechanism is a sealed bag called a Security Tamper-Evident Bag, or STEB. Understanding exactly how this works — and, critically, where it fails — is the difference between arriving home with your purchase and watching it confiscated at a connecting airport.

What Is a Security Tamper-Evident Bag (STEB)?

A Security Tamper-Evident Bag (STEB) is a specially designed, sealed clear bag used by airport duty-free retailers. When you buy a bottle of wine or a litre of spirits at a duty-free shop past the security checkpoint, the retailer places the item in a STEB, seals it, and includes your receipt inside the bag.

The STEB is:

• Clear: so security can see the contents without opening it
• Tamper-evident: the seal cannot be reopened and resealed without visible damage
• Receipt-included: proof of purchase at or after the airside security checkpoint is sealed inside

A properly sealed STEB signals to security officers that the liquid was bought at a point past the original security checkpoint and has not been removed from the controlled airside area. This is the legal basis for the exemption: the chain of custody between the duty-free sale and the boarding gate is verifiable.

The STEB Exempts the Liquid from the 100ml Rule

At the original departing airport, a correctly sealed STEB exempts the contents from the 100ml carry-on rule. You may carry a 1-litre whisky bottle, a 750ml bottle of wine, or a full-size bottle of perfume in your carry-on bag if it is sealed in a valid STEB from the duty-free shop at that airport.

This is not a loophole — it is the intended design. ICAO (the International Civil Aviation Organization) created the STEB standard specifically to allow duty-free purchases to be carried through security while maintaining the security integrity of the liquid screening system.

Practical buying advice:

• Confirm the retailer uses proper STEB bags before purchasing large liquid items
• Keep the receipt visibly inside the bag and do not open the bag before boarding
• Do not consolidate items from multiple purchases into a single STEB — each purchase should be in its own sealed bag with its own receipt

The Connecting Flight Problem

Here is where duty-free liquids become genuinely complicated. If your itinerary includes a connection and you pass through a second security checkpoint at the connecting airport, the STEB may not be accepted.

Why this happens:

Not all airports or transit security checkpoints accept STEBs from other airports. Security policies at connecting airports are set by the national aviation authority of that country, not by the airline or the original duty-free retailer. A STEB sealed in Dubai may not be recognized as valid at London Heathrow's transit security. The receipt inside shows when it was purchased, but if the connecting airport's policy is to reject STEBs older than 24 hours, or to reject STEBs from certain origin countries, the contents will be confiscated.

Connecting airports with known STEB complications:

• UK airports (Heathrow, Gatwick, Stansted): Transit security at UK airports has historically been inconsistent about STEB acceptance. UK government guidance recommends packing duty-free in checked luggage for connections.
• US airports (any hub): US transit passengers who arrive from an international origin and continue to a domestic flight typically pass through a second security checkpoint. US TSA will apply the standard 100ml rule even to sealed STEBs from the origin airport — the US does not recognize the STEB exemption for re-screening at domestic connections.
• EU airports: EU transit security generally accepts STEBs purchased at other EU airports, but acceptance of STEBs from non-EU airports varies by airport and officer.

The safest approach for connecting flights:

If you have any connection and the purchase is valuable, place duty-free alcohol in checked luggage at your origin airport rather than carrying it on. If you are determined to carry it on, verify the specific policy of your connecting airport's transit security before purchasing.

Quantity Limits: What You Can Actually Keep

Even if your duty-free purchases survive all security checks on the plane, there are customs allowances at your final destination that limit what you can bring home duty-free. Amounts above the limit are not confiscated but are subject to import duty.

Destination	Wine Allowance	Spirits Allowance
United Kingdom	4 litres (still wine)	1 litre (spirits over 22% ABV)
United States	1 litre total	1 litre total
European Union	4 litres (still wine)	1 litre (spirits over 22% ABV)
Australia	2.25 litres total alcohol	2.25 litres total
Canada	1.5 litres wine or 1.14 litres spirits	varies by province

These are the duty-free allowances — the quantity you may bring in without paying import duty. Amounts above these limits are not prohibited, but you will owe duty on the excess. The rate varies by country and product type.

At the US customs declaration stage, any alcohol above 1 litre must be declared and is subject to federal and state duties. Failure to declare alcohol above the limit risks confiscation and civil penalties.

Perfume and Other Liquid Duty-Free Purchases

The STEB rules apply equally to perfume and other liquid duty-free items, not just alcohol:

• A 100ml bottle of perfume purchased after security and sealed in a STEB is exempt from the carry-on liquid rule at the origin airport
• The same connecting flight problems apply — the STEB may be rejected at connecting security checkpoints
• Perfume above personal-use quantities may be subject to customs declaration at destination

For high-value perfume purchases, the same guidance applies as for alcohol: if connecting, consider carrying a small bottle in your carry-on liquids bag (within the 100ml rule) and checking larger purchases.

Alcohol in Checked Luggage: Quantity Limits

If you choose to pack duty-free alcohol in checked luggage:

• Up to 24% ABV: No carry quantity limit for checked luggage
• 24% to 70% ABV: Maximum 5 litres per person in checked luggage
• Over 70% ABV: Not permitted in checked luggage

Most commercially sold spirits (40–46% ABV) fall in the 24–70% category. Five litres in checked luggage covers most traveler needs. Very high-proof spirits (cask strength whisky at 60%+ or overproof rum) may still be under the 70% ceiling, but should be verified.

Checked luggage alcohol must be in securely sealed, retail packaging. Bottles packed in checked luggage should be wrapped to prevent breakage — airport baggage handling is not gentle.

The Practical Decision Tree

1. No connecting flight: Buy duty-free liquids in STEB, carry on, no problem.
2. Connecting flight at a single EU-to-EU airport: STEB likely accepted; lower risk.
3. Connecting through UK, US, or long-haul hub: High risk of STEB confiscation at transit security. Pack in checked luggage instead.
4. Unsure about your connecting airport: Pack in checked luggage. The cost of losing a £40 bottle of whisky to confiscation is not worth the convenience.
5. Final destination quantity allowance: Check before purchasing more than 1 litre in the US, 2.25 litres in Australia, or 1 litre spirits plus 4 litres wine for UK/EU.

Summary: Duty-Free Liquids on Planes at a Glance

Duty-free liquids purchased after the security checkpoint and sealed in a Security Tamper-Evident Bag (STEB) are exempt from the 100ml carry-on rule at the origin airport. The STEB must remain sealed with the receipt inside. The major complication is connecting flights: US, UK, and many other transit security checkpoints may confiscate STEB-sealed items at a second screening. The safest strategy for any itinerary with a connection is placing duty-free alcohol in checked luggage. Customs allowances at destination limit duty-free imports — the UK and EU allow up to 4 litres of wine plus 1 litre of spirits; the US allows 1 litre total. Alcohol in checked luggage is limited to 5 litres per person for items between 24% and 70% ABV.