Do you have to go through customs on a layover? When you have a layover, whether or not you have to go through customs depends on various factors, including your departure and arrival countries, the airports involved, and the duration of your layover. For international layovers in a different country than your final destination, there's a high chance that you'll have to complete customs and immigration procedures.
Usually, travellers on layover flights are required to go through customs and immigration upon their initial entry point. To streamline this procedure, you may want to contemplate applying for the Global Entry program.
For overseas layovers in European countries, the customs and immigration process can vary based on whether both the layover and final destination countries are within the Schengen Zone.
If both countries are Schengen Zone members, you can bypass customs and immigration. For example, when travelling from France to Mexico with a layover in Spain, you only need to complete these formalities once, upon reaching Mexico.
However, if you're travelling from a Schengen member country to another EU nation outside the Schengen area, you won't encounter customs restrictions but will undergo immigration procedures (e.g., travelling from Ireland to Germany or vice versa).
If you're departing from an EU country to a non-EU Schengen country, you'll need to clear customs but not immigration (e.g., Switzerland to France or vice versa).