I have watched cousins make every mistake this article covers. Some cost them money. Some cost them time. A few cost them the trip itself.
The thing about renting a car in Ireland is that the system looks familiar — you have rented cars in North America, you know how it works — and then you discover that the familiar system has different rules here. The excess is not the same. The deposit is not the same. The insurance you brought from home is not recognised. And the roads, which have nothing to do with the rental contract, are the thing that catches most people off guard.
Here are the ten mistakes I see most often, in the order they tend to happen on a trip.
1 — Booking the Wrong Transmission
This is the one that catches more visitors than anything else. You drive an automatic at home. You assume an automatic in Ireland is the default. It is not.
The majority of cars in Ireland are manual. Rental fleets carry automatics, but they are a smaller proportion and they book out weeks in advance in summer. If you show up at the desk expecting an automatic and the agency has run out, you will be offered a manual or a significantly more expensive upgrade.
The real cost of a manual you cannot drive is not the upgrade — it is the burnt clutch on a hill start in Kerry. A clutch replacement on a rental car runs upwards of €2,500. That is not covered by any insurance, because it counts as driver negligence.
How to avoid it: Book your transmission at the time of reservation, not at the desk. My Irish Cousin guarantees the transmission you order — if you book an automatic, that is exactly what you get. How to Choose the Right Rental Car in Ireland covers the full decision on transmission and vehicle size.
2 — Not Understanding the Insurance Excess
The single biggest financial risk of renting a car in Ireland is not the rental cost. It is the excess.
A standard Irish rental contract carries an excess of €1,500 to €3,000. That means if a stone chips the windscreen on the M50, or a gate swings into the wing mirror at a B&B car park, you are liable for the full amount up to that excess. Super CDW at the desk reduces it — typically to €500 to €1,000 — but adds €15 to €25 per day to the rental cost.
How to avoid it: Book with a company that includes zero excess in the base rate. Car Rental Insurance in Ireland: CDW, Super CDW & Excess Explained breaks down exactly what each level of cover means and what you do not need to buy at the desk.
3 — Relying on Third-Party Insurance
Your credit card offers rental car insurance. Your travel insurance offers rental car insurance. You assume either one covers you at the Irish rental desk.
They do not.
Irish rental companies do not recognise third-party insurance policies held by the renter. The rental contract will still offer you Super CDW at the desk, and the excess on that contract will still apply regardless of what your credit card says. You will be asked to sign a waiver or pay for the desk cover. There is no way around this at the pickup counter.
How to avoid it: Ignore what your credit card or travel insurance says about rental car cover. Choose a rental company based on what is included in their contract, not on what you think your existing policies cover.
4 — Not Checking the Fuel Policy
Rental fuel policies vary more than most visitors expect. Full-to-full is the most common: you receive the car with a full tank and return it full. If you return it less than full, the agency charges a premium per litre plus a refuelling service fee that can be significant.
Some agencies use a full-to-empty model where you pre-pay for a full tank and return the car empty. This works in your favour only if you actually use the full tank. Most visitors do not, and the unused fuel is not refunded.
How to avoid it: Know the policy before you sign. Full-to-full is straightforward and fair if you fill up at a station near the return location. Check the fuel type at pickup — diesel and petrol nozzles look similar at an unfamiliar station, and the wrong fuel costs upwards of €1,500.
5 — Underestimating the Roads
This is the mistake that does not show up on the rental contract but affects everything else.
Irish roads are narrower than what most North American drivers are used to. The R roads are single-track with passing places. The N roads are two-way but often barely wider than a car and a half. Hedgerows and stone walls sit right at the edge of the tarmac. Tour buses and tractors appear around blind corners. And you are driving on the left, which means your instinctive lane position is wrong for the first hour.
How to avoid it: Choose a smaller car. A compact hatchback is easier on narrow roads than a full-size saloon or SUV. Trust your peripheral vision rather than staring at the white line. And if you are not confident with a manual, book an automatic — removing the clutch from the cognitive load makes a real difference. Driving in Ireland: Road Rules & Tips for Visitors (2026) covers roundabouts, speed limits, and what the Gardaí expect.
6 — Booking a Car That Is Too Big
Related to the road width problem: visitors routinely book cars that are too large for Irish roads.
A full-size SUV that feels comfortable on a US interstate is a liability on the R558 in Clare. Not because the car cannot handle it, but because the margins for error disappear. The car occupies the full lane, the stone walls are right there, and passing places require careful judgement. Parking in small-town car parks becomes a negotiation with the available space.
How to avoid it: A compact or mid-size hatchback is the right vehicle for Irish roads. It handles the narrow lanes, parks easily, and is more fuel-efficient. If you need space for luggage, a mid-size estate car gives you the boot capacity without the width of an SUV.
7 — Forgetting about Tolls
Ireland's toll roads are concentrated around Dublin and on major inter-city routes. The M50 ring road around Dublin is barrier-free and uses eFlow automatic number plate recognition. If you drive on it without a toll tag or a pre-paid account, a letter with an admin fee arrives at the rental company, which passes the cost to you.
Some rental companies charge an additional administrative fee per toll transaction on top of the toll itself. Over a two-week trip crossing the M50 multiple times, these fees can add up significantly.
How to avoid it: Ask whether tolls are included in your rental rate before you book. My Irish Cousin includes all tolls — no toll tag fee, no admin charge per barrier. Taking a Rental Car from Ireland to Northern Ireland covers what happens at the border tolls as well.
8 — Not Planning the Drop-Off
The Dublin Airport return is straightforward once you know where you are going. If you do not, it adds stress to the last hour of your trip.
The My Irish Cousin return is at the Eastlands Car Hire Facility in Cloghran, Swords — a five-minute shuttle from the terminal. If you are returning at a busy time, allow an extra fifteen minutes for the shuttle queue. If you are returning outside staffed hours, check the drop-box procedure in advance.
How to avoid it: Save the return location address before you leave. Fill the tank at a station near the airport, not at the airport forecourt where prices are higher. Allow time for traffic on the M50 — Dublin peak traffic is real. Dublin Airport Car Rental: Pickup Guide & What to Expect covers the full arrival-to-key-turn process.
9 — Arriving without the Right Documents
The documents you need to rent a car in Ireland are straightforward, but the rules are strict.
You need a full, valid driving licence issued in your country of residence. A paper licence is not accepted. A photocopy is not accepted. A provisional or temporary licence is not accepted. If your licence is not in English or does not use the Latin alphabet, you need an International Driving Permit alongside it.
How to avoid it: Check your licence before you travel. If you have a paper licence or a provisional licence, resolve it before your trip. Bring the physical card — a photo on your phone will not be accepted. What Documents Do You Need to Rent a Car in Ireland? covers the full list.
10 — Booking Late in Peak Season
This is the mistake that compounds every other mistake on this list.
Booking a rental car a week before your July trip means you take whatever is left. That could be a manual when you wanted an automatic. That could be a full-size SUV when a compact would suit the roads better. That could be a higher rate with a larger excess because the lower-tier cars are gone.
Summer in Ireland is a small island with a concentrated tourist season. The rental fleet is finite. By June, the best-value cars at the best rates are booked. By July, availability drives the market, not price.
How to avoid it: Book as soon as your flights are confirmed. The best rates and the best transmission choices are available three to four months out. If you are planning a trip in high season and the car you want is already gone, consider Celtic Vacations — their self-drive packages include a pre-booked car in the overall itinerary, which can unlock availability you cannot get booking directly.
The One Mistake That Underlies All Ten
Every mistake on this list traces back to the same root: assuming that renting a car in Ireland works the same as renting a car at home.
It does not. The transmission norms are different. The insurance structure is different. The roads are different. The fuel policies are different. The deposit rules are different. None of it is difficult once you know what to expect — but the assumptions you bring from North America will cost you if you do not check them at the door.
Book the right transmission. Understand the excess. Ignore your credit card insurance. Drive a car that fits the roads. And book early enough that you have a choice.
Ready to get it right from the start? Request a quote from My Irish Cousin — zero-excess included, transmission guaranteed, tolls covered. For the full picture, Renting a Car in Ireland: Complete 2026 Guide ties everything together from choosing the car to driving home.
