Cross-Border Car Rental from Herceg Novi. Pick up in Herceg Novi and you are the best-placed town in Montenegro for a border run — the western gateway. The Croatian frontier is a short hop up the coast and Bosnia (Trebinje) is inland, and neither needs the Lepetane-Kamenari ferry that Kotor and Budva drivers plan around, because Herceg Novi already sits on the west side of the Bay of Kotor. Yes, you can cross with the rental company's written cross-border authorization (and usually a cross-border fee). The Green Card myth: for Croatia, Bosnia and Serbia a Green Card is NOT legally required — Montenegro is in the Multilateral Agreement License-Plate Subsystem, so the plate proves insurance; the cross-border fee is a commercial surcharge, not a border tax. Green Card is mandatory only for Albania (buyable at Bozaj about €15/14 days). Kosovo is outside the Green Card system (border TPL about €15/15 days; often banned). Documents at any border: the ORIGINAL vehicle registration (copies/scans/photos are rejected — the #1 turn-back reason), rental agreement plus written cross-border authorization, and a passport (EES biometric checks now apply on the Croatian/Schengen side). Herceg Novi to Croatia: Debeli Brijeg / Karasovici is only about 15 km / 25 min, open 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. Vitaljina / Kobila is 24/7 passenger cars only, skipping the bus queues. Herceg Novi to Bosnia: Trebinje about 40 km / 50 min via Sitnica / Zupci, a joint border post since April 2025 (one stop, shorter queues); Mostar is further (about 120 km). 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 €40 flat (Kosovo not included); MTL Rent €50 flat plus a 200 km/day limit, €0.10/km over; CarWiz €50 flat; Stella Car €25 flat (Kosovo banned). Practical tips: never cross without written authorization (GPS flags it, voids insurance, AbbyCar €500 penalty); one-way abroad is rare; Serbia has a strict 0.03% alcohol limit and needs a vignette; winter tyres 15 Nov-1 Apr on mountain sections, minimum 4.0 mm tread.