Some ports and airports only have one exit and a red point phone where you declare goods.

If you receive an HMRC letter saying it thinks you are running a business and have failed to declare this on your tax return, make sure you have all the facts and records of all transactions. you have 10,000 euros or more (or equivalent) in cash. When entering the UK from a non-EU country, you must make a declaration to customs if: you exceed your allowances, which includes up to one litre of spirits, 200 cigarettes and a maximum of £390 worth of perfume and souvenirs.
( As with the change in tobacco allowances, you can now make up your alcohol allowance from a mix and match of alcohol products.

In many airports, immigration is a mandatory process that involves speaking with an immigration officer who stamps your passport, while customs is an optional process; if you have nothing to declare, you don’t need to speak with an officer. If the customs department seizes your money, a formal seizure notice will be issued by U.S. Customs. Declaring goods to customs You must tell customs (known as ‘declaring’) on arrival in the UK if you have goods: over your duty-free allowance; that are banned or restricted; that you plan to sell; Use the red channel at customs if you have something to declare. If you’re travelling from the Channel Islands, you need to clear UK customs but you don’t go through passport control. You can find the official statement on this at the US Customs and Border Protection website. For example, you would declare alterations made in a foreign country to a suit you already owned, and any gifts you acquired outside the United States. Customs will inspect the paperwork you have provided, and then decide how much duty and tax will be payable by the recipient. People with Second Homes in the UK Going through Customs Most UK ports and airports have three exits or ‘channels’: the red, green and blue channel. If you enter or leave the EU with € 10 000 or more in cash, you must declare it to Customs. €10,000 or more If you’re carrying cash or goods with the equivalent value of €10,000 or more, stop by the red customs exit to declare. If you're declaring more than $10,000, have your copy of a FinCen Form 105, a document issued by the Department of Treasury, ready for the customs officials. You will not have to pay duties or taxes, but you must declare it on the Customs Declaration form.

You will need to prepare paperwork which is called a customs invoice, which declares what items you are shipping, the quantity, the value, and why you're sending them, ParcelCompare helps produce this paperwork. the goods are for commercial use. 1 litre of spirits or strong liqueurs over 22 per cent alcohol by volume, or 2 litres of fortified wine (such as port or sherry), sparkling wine or other liqueurs. You can go through immigration without your luggage, but customs will be located after baggage claim.

If you declare you have food, you have met your legal requirement, and then an agent can decide if the food you have is permissible or if it needs to be confiscated.

EU Cash Declaration Form. The rules for what you must declare at customs abroad will vary by country, but the general rule still works -- better to declare it to avoid confusion or hang-ups.
Declare It Abroad. You must tell customs (known as ‘declaring’) on arrival in the UK if you have goods: over your duty-free allowance; that are banned or restricted; that you plan to sell We provide links to the forms where these have been submitted to us by the Member States.