Additional-driver rules explained

By the Viamo editorial team · Editor Terje Moy · Last updated July 2026 · 5 min read

Sharing the driving on a road trip is one of the most sensible reasons to add a second person to a rental agreement, yet it's also one of the most commonly skipped steps — either to save the extra fee or simply because nobody thought about it until they were already swapping seats on the motorway. The additional driver fee is usually modest; the risk of not paying it, if something goes wrong, generally isn't. Here's how the rule actually works, what it costs, and why it matters more than it looks.

What "additional driver" actually means

Every rental agreement names a primary renter — the person who books, presents their licence and card at the desk, and signs for the vehicle — plus, optionally, one or more additional drivers who are also authorised to drive the car under that same agreement. Anyone driving the car who is not the primary renter and not listed as an additional driver is, technically, an unauthorised driver, regardless of how well-intentioned the arrangement is or how briefly they take the wheel.

The fee: usually modest, sometimes free

Most companies charge a daily or flat fee to add a second driver, though it's typically a small proportion of the overall rental cost rather than a major expense. Some loyalty programmes and certain rate types waive the fee for a spouse or partner, or occasionally for any additional driver, as a program benefit — check your specific booking's terms and any loyalty status you hold, since this is one of the more commonly overlooked ways to reduce the cost of adding a second driver.

What's required to add someone

• A valid driving licence for the additional driver, meeting the same requirements as the primary renter — including an International Driving Permit where one would otherwise be required. See our International Driving Permit guide if either driver's licence needs one for your destination.
• Presence at the desk, in most cases — many companies require the additional driver to be physically present at collection to show their licence and sign the agreement, rather than being added purely on paperwork or a phone call in advance.
• Meeting the same age and experience requirements as the primary renter — an additional driver under 25 can trigger the same young-driver surcharge as if they were the lead renter, since many companies apply the fee based on the youngest driver on the agreement, not just the primary one.

Why an unlisted driver is a real risk, not just a technicality

This matters most on trips where driving is genuinely shared — a long road trip between two or more people, or a family holiday where a partner might take over for part of the drive. The modest additional driver fee is far cheaper than discovering, after an accident, that none of your cover applies because the person behind the wheel wasn't on the agreement.

Adding a driver after collection

If your plans change mid-trip and someone needs to be added who wasn't on the original booking, contact the rental company directly — most allow this at a local branch, sometimes with the same fee applied on a pro-rata basis for the remaining days. It generally cannot be done informally by simply calling to mention it; the additional driver typically still needs to appear in person with their licence at some point to be properly added to the agreement, so plan this before the swap needs to happen, not after.

Additional drivers and cross-border trips

If your trip crosses a border in the hire car, confirm that any additional driver is covered for the same cross-border permission as the primary renter — this isn't always automatic, and some companies handle cross-border authorisation and additional-driver authorisation as separate line items on the agreement. See our guide to crossing borders in a rental car for how that authorisation generally works, and confirm both pieces are in place for every driver who might take the wheel across the border.

Family members: sometimes an exception

A number of rental companies waive the additional driver fee specifically for a spouse or registered partner living at the same address as the primary renter, though the exact definition and required proof (a shared address on a licence, for instance) vary by company. This exception generally does not extend to other family members — adult children, siblings or parents typically still incur the standard fee unless a specific loyalty programme states otherwise. Ask directly at booking or check the terms rather than assuming a family relationship qualifies automatically.

How to handle it at booking versus at the desk

Adding a known additional driver at the time of booking, rather than waiting until collection, is generally simpler and avoids any risk of the desk being unable to accommodate the addition on a busy day — though most companies do allow it at the desk as well, provided the driver is present with the right documents. If you already know a second person will share the driving, add them when you book; if plans are still uncertain, you can usually still add someone at the desk on the day of collection, so it's rarely a reason to delay booking the car itself.

Frequently asked questions

How much does it typically cost to add an additional driver?

It's usually a modest daily or flat fee, a small proportion of the overall rental cost. Some companies waive it for a spouse or registered partner at the same address, and certain loyalty programmes reduce or remove it entirely.

What happens if an unlisted driver has an accident in a hire car?

The rental company's damage cover, including any excess waiver you purchased, can be voided for that incident, potentially leaving you liable for the full repair cost rather than just the excess. Always add anyone who might drive, even briefly.

Does the additional driver need to be present when the car is collected?

Usually, yes — most companies require the additional driver to show their own valid licence and sign the agreement in person, either at collection or when added later at a branch, rather than being added purely over the phone.

Does adding a younger additional driver trigger a young-driver surcharge?

Often, yes — many companies apply the young-driver fee based on the youngest driver on the agreement, whether that's the primary renter or an additional driver, so adding someone under 25 can add both the additional-driver fee and a young-driver surcharge.