1. Start with the rental agreement, not the map
A route can look like a simple line between Dubrovnik and Kotor, Split and Mostar, or Podgorica and Tirana. The supplier sees a different question: where is the vehicle insured, which countries are allowed, and what evidence will the driver carry at the border? Those conditions vary by supplier, vehicle class, pickup country, dates and sometimes the intended return location.
Tell the rental company every country you may enter, including a country you might only cross on the way to another destination. Do not rely on a verbal “it should be fine”. Ask for the written authorisation, the cross-border charge, the required insurance document and any restrictions on luxury, electric, commercial or special-category vehicles. If your plan changes after pickup, contact the supplier before crossing rather than assuming you can regularise the trip at the next border.
Permission
The supplier must approve the countries and route. A border being geographically close does not make it contractually permitted.
Evidence
Carry the rental agreement, driver details, registration evidence and whatever insurance or authorisation document the supplier specifies.
Return
International one-way returns are a separate product decision. Confirm availability, vehicle movement and charges before booking.
2. Documents and insurance at the crossing
The driver normally needs a valid passport or travel document, the driving licence accepted for the trip, the rental agreement and the vehicle or insurance evidence supplied by the rental company. An international driving permit may be relevant to the driver's nationality, licence format or destination; check the current rule for the exact trip instead of treating it as a universal requirement.
Some travellers refer to a Green Card or International Motor Insurance Card (IMIC). The name, format and acceptance can change, and a document that proves insurance does not by itself prove that the rental company has authorised the vehicle to cross a border. Ask the supplier what it will issue, keep a digital copy and carry the original when requested.
Read the policy exclusions as carefully as the headline cover. Damage, theft, roadside assistance, tyres, glass, ferry transport and recovery can be treated differently outside the pickup country. If an accident occurs, follow the supplier's reporting procedure and local authority requirements immediately; do not negotiate a private settlement that prevents the company from inspecting the vehicle.
