You can carry any amount of cash through Heathrow, but if you are travelling to or from a country outside the UK with £10,000 or more, you must declare it to UK customs. Miss the declaration and Border Force can seize the entire amount, and you may need to pay a penalty of up to £5,000 to get it back. Checked September 2026.
What counts as cash for this rule
The £10,000 threshold is not limited to banknotes and coins. HMRC's definition of cash for declaration purposes also includes bearer bonds, travellers' cheques, and cheques that are signed but not made out to a specific person or organisation. It applies per journey between Great Britain and a country outside the UK, so as Heathrow's international, long-haul-heavy route network makes this rule relevant to a large share of its passengers, in both directions.
The £10,000 threshold applies to groups, not just individuals
If you are travelling as a family or group and your combined cash comes to £10,000 or more, you still need to make a declaration, even if no single person in the group is carrying that much individually. This catches out travellers who deliberately or accidentally split cash between bags or people to stay under the limit each, since HMRC looks at the total carried by the travelling party, not each person separately.
How to declare cash before flying from Heathrow
| Step | Detail |
|---|---|
| When you can declare | Online from up to 72 hours before you travel |
| Leaving the UK | You must declare before you go |
| Arriving in the UK | Declare before you travel, or at customs on arrival |
| No way to declare on site | Call the Customs and International Trade Helpline on 0300 322 9434 (24 hours) |
Declaring online gives you a reference number that you may be asked to show. If you would rather not declare online, you can do it over the phone using the same helpline. If you need to change money for your trip rather than carry cash, see the guide to currency exchange at Heathrow for the alternatives.
What happens at Heathrow if you are arriving with cash to declare
Follow the "goods to declare" or red channel signage after baggage reclaim in your terminal, and tell a Border Force officer that you want to declare cash. You may be asked to use a courtesy phone to get through to the relevant team, and you will either fill in a paper form or have your declaration taken directly by the officer.
What information you need to make a declaration
A cash declaration asks for details of who is carrying the money, who owns it and who it is going to, including passport or ID details and an address. You also need to describe your journey, including any transit countries and your flight numbers, state the amount and type of cash, explain where it came from (for example, savings or the sale of a property), and say what it will be used for.
Penalties for not declaring
If you should have declared cash and did not, a Border Force officer can seize the entire amount you are carrying, not just the excess over £10,000. Getting it back can mean paying a penalty of up to £5,000, which is deducted from the seized cash before the rest is returned. If customs authorities have reasonable grounds to suspect the money is linked to a crime, they can hold it for 48 hours without a court order, and longer than that only with one. If you disagree with a penalty, you can appeal in writing to HMRC's Fraud Investigation Service within 30 days of the penalty notice.
Connecting through Heathrow to or from Northern Ireland
If your Heathrow itinerary connects onward to or from Northern Ireland, the threshold there is €10,000 or more (or the equivalent) rather than £10,000, and the direction of travel matters: you need to declare cash carried into Northern Ireland from Great Britain, but not cash carried the other way. For the standard case of flying between Heathrow and a non-UK country, the £10,000 Great Britain threshold described above applies.
Why this matters for Heathrow specifically
As one of the world's busiest hubs for long-haul and business travel, Heathrow sees a wide range of legitimate reasons for carrying large sums, from business transactions and property purchases abroad to wedding gifts, inheritance money and family support payments. None of these are exempt from the declaration requirement simply because the purpose is legitimate. Since Heathrow's passenger mix includes many connecting itineraries, it is also worth checking whether your specific route counts as travelling "to or from" the UK for these purposes if your journey is unusually complex, rather than assuming a straightforward transit exempts you. Cash rules are separate from the duty-free goods allowance for alcohol, tobacco and other purchases, and separate again from checking whether you need a passport for a domestic UK flight if part of your journey is UK-only.
The takeaway
The rule for Heathrow passengers is straightforward: £10,000 or more in cash, cheques or bearer bonds travelling to or from a country outside the UK needs a declaration, made online up to 72 hours ahead, over the phone, or at the red channel on arrival. Skipping it risks the whole sum being seized rather than just the amount above the limit.