A ferry booking feels like the easy part of a trip: choose a route, choose a sailing, pay, then forget about it until the morning you drive to the port. Then something shifts. A work commitment moves, a hire car arrives longer than expected, a flight connection slips. Suddenly the ticket you bought is quietly assuming nothing will change. These are the five booking errors that cost ferry travellers the most, and how to sidestep them.

1. Booking in the wrong name

The passenger name on a ferry booking is not a formality. On most routes it has to match the photo ID or passport presented at check-in, and on some fares the name cannot be changed at all, which means cancelling and rebooking, usually at a higher price. A familiar short form causes more trouble than people expect: a passport reading David will not always be accepted against a ticket for Dave.

It takes two minutes to get right.

1. Type names exactly as they appear on the passport or ID, including hyphens and accents.
2. Follow the operator's instruction on middle names rather than guessing; some systems want them, others do not.
3. If you are paying for someone else's trip, put their details in the traveller fields and yours in the payment fields.
4. Read the confirmation email when it arrives. Some operators allow small corrections for a short period after booking; after that, the fare rules take over.

2. Guessing your vehicle's size

On many routes, vehicle fares are banded by length and height, and the gap between bands is real money. It is tempting to round down, or to book for the car you usually drive and then turn up in a borrowed estate with a roof box and a bike rack. Under-declaring a vehicle tends to end one of two ways: an upgrade charge at the port, often at the on-the-day rate, or no space at all on a full sailing.

Measure the whole outfit before you book: bumper to tow bar, roof box and bars included, and the full length of a caravan, trailer or motorhome with any rack fitted. If a hire car or a courtesy vehicle is likely, remember that vehicle details can usually be amended later, provided you do it before the cut-off, but you need the measurements to amend them. Motorcycles, bicycles and trailers sometimes sit outside the standard car bands, so check how they should be declared.

3. Buying the cheapest fare when your plans might move

Ferry pricing works like air pricing in one important way: the lowest fares carry the tightest conditions. A saver ticket may be non-refundable, non-transferable and amendable only up to a set number of hours before departure, often 24 or 48, with a fee on top. A flexible fare costs more on the day you book and considerably less on the day your plans change.

Read the fare rules before comparing prices, not after. The questions worth asking:

• Can I change the date and time, and by when? Is there a fee?
• Can I change the passenger name?
• If I cancel, do I get a refund, a credit note, or nothing?
• Does the fare include a cabin, a seat reservation or a meal, or are those extras?

If there is any chance the trip will move, whether because of a wedding, a house sale, a flight connection or an exam timetable, the flexible fare is often cheaper in practice. If your dates are genuinely fixed, take the saving and enjoy it.

4. Leaving the add-ons until the last week

Cabins, pet-friendly spaces, accessible cabins and some seat or lounge reservations are sold separately from the vehicle or foot passenger space, and they are finite. On a popular summer crossing, the car deck can show availability long after the last pet space or the last family cabin has gone, and turning up at the port hoping to buy one is a gamble.

Book what you need alongside the crossing: a cabin if the sailing is overnight or long, a pet space if an animal is travelling, and an accessible cabin early if anyone in the party needs one, since those go first on many routes. If you are travelling with a pet, check the operator's rules on paperwork, exercise areas and whether the animal stays in the vehicle or in a designated area, as requirements differ between routes and countries. For anything involving animal health certificates or vaccination timing, speak to your vet well before you travel.

5. Assuming the port, terminal and check-in window will sort themselves out

Three things catch people out here. The first is the check-in window. Vehicle passengers are usually asked to check in well ahead of departure, often an hour or more, while foot passengers may have a shorter window. The exact figure is in your booking confirmation and varies by route and operator, so read it and work backwards, adding a buffer for roadworks, holiday traffic and port queues.

The second is the port itself. Some crossings sound similar but leave from different places, and some ports operate more than one terminal. Check the postcode rather than the town name, and check it again the night before.

The third is time. Arrival times on a timetable are normally shown in local time at the port where you arrive, so a route that crosses a time zone moves your clock forward. Allow for that when booking onward travel, and avoid building a tight connection on the advertised arrival time alone.

Before you pay: a five-minute check

Most of these mistakes are caught by reading the confirmation properly rather than skimming it. Run through this list before you close the payment page, and again when the email lands.

• Names spelled exactly as they appear on travel documents.
• Vehicle type, length and height, with roof boxes, racks and trailers included.
• Route, port, terminal, date, departure time, and whether the arrival time is local.
• Fare rules: amendment cut-off, cancellation terms, name-change policy.
• Add-ons: cabin, pet space, accessibility needs, meals, seat reservations.
• Check-in time and the documents you will need at the port.

Care taken at the booking stage is far cheaper than a rebooking at the port. If anything in the fare rules is unclear, ask the operator in writing before you pay. A quick message to customer service creates a record of what you were told and usually gets a straight answer, which is worth more than a few pounds saved on a fare you cannot use.

Photo: Svetlana Tumina / Pexels