Taking a Kotor Rental Across the Border. Yes, you can take a rental car picked up in Kotor across most of Montenegro's borders — but only with your rental company's written cross-border authorization, and only for the countries that company permits. The most common run is Kotor to Dubrovnik, Croatia: ~90 km / 2 hours, shortened by the Lepetane–Kamenari ferry (€5.00 flat per car, year-round since Feb 2025, ~10 min crossing, saving ~30 km and ~45 min). The cross-border fee is a commercial surcharge for extended insurance cover, NOT a border tax. Do you legally need a Green Card? For Croatia, Bosnia & Herzegovina and Serbia it is NOT legally required — Montenegro is in the Multilateral Agreement License-Plate Subsystem, so the number plate itself proves insurance. A Green Card is mandatory only for Albania. Kosovo is outside the Green Card system and needs border third-party insurance (indicatively ~€15 for 15 days); many companies ban Kosovo outright. Documents at every border: the ORIGINAL vehicle registration (photocopies/scans/phone photos are rejected), the rental agreement plus written cross-border authorization, a passport (EES biometric checks now apply on the Croatian/Schengen side), and a paper Green Card for Albania. Kotor to Croatia: cross at Debeli Brijeg / Karasovići (24/7; Jul–Aug 10:00–14:00 queues reach 2–5 hours, off-season 15–30 min; cross before 08:00 or after 20:00), or use Vitaljina / Kobila (24/7, passenger cars only — no buses/trucks, skipping the tour-bus queues). Kotor to Bosnia: Trebinje ~90 km / 1.5h, Mostar ~180 km / 3h 15m, main crossing Sitnica / Zupci (a joint border post since April 2025). Serbia has a strict alcohol limit (0.03%, effectively zero for novice and professional drivers) and needs a vignette. Cross-border fees by company (indicative, Summer 2024, verify at booking): Europcar Montenegro €6.05/day capped at €60.50 (Kosovo/Greece/Bulgaria/Romania not allowed); Sixt Montenegro €40 flat (Kosovo not included); MTL Rent €50 flat + a 200 km/day limit, €0.10/km over; CarWiz €50 flat, all countries; Stella Car €25 flat, Kosovo banned. Expect roughly €25–€70 flat or ~€6/day capped near €60. Practical tips: never cross without written authorization — GPS tracking flags it automatically, voids insurance, and AbbyCar applies a €500 penalty. One-way drop abroad is rare (only some large chains, at a premium). Winter tyres are legally required 15 Nov – 1 Apr on snowy/mountain sections, minimum 4.0 mm tread or the tyre counts as summer and can void CDW.