SIPP codes are the four-letter codes used in car hire to describe the vehicle category. They help suppliers and brokers communicate size, type, transmission, fuel or air conditioning in a compact format.
A SIPP code does not normally guarantee an exact make or model. It describes a category, so the car shown in search results may be an example such as ?Ford Focus or similar?. On gocarhire.co.uk, always read the vehicle details and supplier conditions before booking.
Understanding SIPP codes helps you compare categories, avoid unsuitable vehicles and choose the right car for passengers, luggage and route. For broader category advice, see our car hire categories guide.
At a glance: car hire SIPP codes
- Four letters: A SIPP code usually describes category, type, transmission or drive and fuel or air conditioning.
- Not an exact model: It normally confirms a class, not a specific vehicle.
- Transmission matters: Manual and automatic can be shown in the code and in the offer details.
- Luggage is not guaranteed: Icons are estimates, so check category carefully.
- Useful for comparisons: Codes help compare similar offers across suppliers.
- Still read conditions: Vehicle examples, deposits and excess can vary by supplier.
What does a SIPP code describe?
A SIPP code is a category shorthand. The first letter usually indicates the size or class, the second describes the vehicle type, the third relates to transmission or drive, and the fourth often indicates fuel or air conditioning.
The code is useful because car hire is usually sold by category, not by exact model. A compact automatic estate and an economy manual hatchback can have very different codes and suitability.
The four parts of a SIPP code
The exact code list is technical, but the practical idea is simple: each letter gives information about the vehicle you are booking.
| Position | What it usually describes | Why it matters |
|---|---|---|
| 1st letter | Vehicle category or size. | Affects comfort, luggage, price and sometimes deposit. |
| 2nd letter | Vehicle type, such as door count, estate or SUV style. | Helps match the car to passengers and route. |
| 3rd letter | Transmission and drive information. | Important if you need automatic or manual. |
| 4th letter | Fuel or air conditioning information. | Useful for comfort and operating expectations. |
Why ?or similar? is important
The model shown beside a SIPP code is normally an example. If the offer says ?Volkswagen Golf or similar?, you are booking a compact category, not that exact car. The supplier can provide an equivalent vehicle in the same category.
This is why you should focus on category features: seats, doors, luggage, transmission, fuel policy and supplier conditions. If an exact feature is essential, such as automatic transmission, check it is clearly stated.
SIPP codes and automatic transmission
Automatic cars can be extremely useful for visitors driving in the UK or for long journeys. However, you should not rely only on a photo. Check the transmission shown in the offer and, if available, the SIPP code information.
For a full booking checklist, read how to hire an automatic car. Confirm again at pick-up before leaving the branch.
Common category decisions
Best for short trips, city driving and limited luggage.
Better for luggage, families, rural routes and longer journeys.
Useful for groups, but check seats and luggage space together.
More comfort, but often higher deposit, excess and stricter conditions.
SIPP codes, luggage icons and real space
Search results may show luggage icons, but these are estimates. A car may seat five people yet have limited boot space. Soft bags fit differently from hard suitcases, and child seats can reduce usable space.
If luggage is important, choose a category with extra margin. For long journeys or family trips, use which car to hire for a long journey before booking.
SIPP code checklist
Before choosing a category
- check passenger count and luggage together;
- confirm manual or automatic transmission;
- read whether the model is guaranteed or only an example;
- compare deposit and excess by supplier;
- check fuel policy and mileage;
- consider road type and parking needs;
- avoid choosing the smallest category if luggage is uncertain;
- confirm the vehicle category at collection.
How SIPP codes help avoid booking mistakes
SIPP codes are useful because they force you to think about the category rather than the marketing image. A photo can make a vehicle look larger, newer or more suitable than the category really is. The code and offer details are a better guide.
This matters when you need automatic transmission, extra luggage space, air conditioning, four doors or a particular body style. If one feature is essential, do not rely on the example model alone. Check the code, the written vehicle details and the supplier conditions before booking.
When to choose a larger category
Choose a larger category if passenger comfort, luggage, child seats or long-distance driving are important. The cheapest category may work for a short city hire, but it can become uncomfortable on a holiday or airport transfer.
A larger category may also mean higher deposit, excess or fuel cost, so compare the full offer. The right choice balances space and cost. SIPP codes help with that comparison, but they should be read together with luggage icons, transmission, fuel policy and total price.
SIPP codes and supplier substitutions
When a supplier gives a different model from the one pictured, the key question is whether it belongs to the same or a higher category. A substitution is normally acceptable if it matches the booked class, but it should still provide the essential features shown in the offer.
If the replacement is smaller, has the wrong transmission or lacks a feature that was confirmed, raise it before leaving the branch. Once you accept the car and drive away, it becomes harder to prove that the supplied category was unsuitable.
SIPP codes at the desk
At collection, the SIPP code can help you judge whether the car offered is a reasonable equivalent. You do not need to argue about a specific model if the category is correct, but you should question a vehicle that is clearly smaller, has the wrong transmission or lacks a confirmed feature.
If the desk proposes a paid upgrade, compare it with what you actually booked. Sometimes an upgrade is useful, but sometimes it is simply a larger or more expensive vehicle than you need.
Final practical check
SIPP codes are also useful when comparing offers across suppliers. Two cars with different example photos may actually belong to a similar category, while two similar-looking photos may hide different transmission, body style or air-conditioning details.
If you are unsure about a category, compare it with the trip rather than the photo: passengers, luggage, roads, parking and driving comfort are more important than the example model.
Conclusion: SIPP codes help, but they do not replace conditions
SIPP codes are useful because they make vehicle categories easier to compare. They help you understand size, type and transmission, but they do not guarantee every feature or exact model.
Use gocarhire.co.uk to compare categories, then read the supplier conditions before choosing the hire car that fits your trip.
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Check SIPP codes, vehicle size, transmission and supplier conditions before booking.
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