Transit is a customs regime whose usefulness lies in allowing the movement of goods in various customs territories under a regime of suspension of taxes and tariffs, such as goods from the United Kingdom destined for Spain, which have to cross the French border with a T1 document to the chosen point of the Spanish customs. In this way, the payment of tariffs and taxes is made in Spain.

It is necessary to identify whether they are products of animal or plant origin, since T1 does not exempt the sanitary or phytosanitary controls from being carried out at the first point of entry into the Union, in that case described above, in France.

This customs regime is also used to export or import merchandise to other countries that make up the European Free Trade Association (EFTA): Switzerland, Norway, Iceland and Liechtenstein.

One of the aspects that must be taken into account to be able to issue this type of document is the obligation of the existence of an individual guarantee for a single operation, or a global guarantee authorization for several joint operations. It is a kind of guarantee whose purpose is to ensure the payment of existing customs duties in the operation.

The holder of the guarantee can be the operator himself or the declarant, in the case of an indirect representation. The latter will also be the debtor of the guarantee.