Grey fleet management software and tools: How to stay compliant, organised, and in control

Grey fleet driving has become the norm for many UK businesses. Sometimes by design, sometimes simply because it evolves that way.

When employees use their own vehicles for work journeys, those vehicles form a grey fleet. And whether they then wish to claim mileage reimbursement from the employer, or mileage relief from HMRC, they need their business driving properly logged and reported. 

This is where grey fleet management software comes into the picture.

What is grey fleet software?

Grey fleet software helps organisations manage business driving that happens in employees’ personal vehicles.

Rather than tracking grey fleet vehicles themselves (as a GPS tracker would), it focuses on tracking, documenting, reporting, and reimbursing business mileage to support compliance with HMRC rules and health & safety obligations.

One of the most important factors in successful adoption is striking the right balance between compliance and control. Organisations need accurate, auditable records, but employees also need transparency and autonomy when using their own cars.

As one operations stakeholder explained in our research:

“People don’t want mileage tracking to feel like big brother. They’re much more comfortable when it’s clear they keep control over their journeys and what gets submitted.”

Source: Sales & Onboarding Call Analysis, 2025

Efficient grey fleet management software gives businesses a structured way to:

• Record business journeys accurately
• Reimburse employees correctly
• Analyse and approve trips and mileage reports 
• Maintain HMRC-compliant mileage logs
• Keep a clear audit trail

The right tools should help support an often-shared ownership across HR, finance, health & safety, and operations, including teams without a dedicated fleet manager, or those managing both personal vehicles and company cars.

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Why grey fleets need management at all

Grey fleet driving can feel more informal than in a commercial fleet or a company car fleet. 

But even when employees drive their own cars, employers are still responsible for compliance, record-keeping, and the duty of care. And employees are still responsible for maintaining a safe vehicle, a valid driver's licence, grey fleet insurance that covers business-related driving, and more. 

Also read: Grey fleet risk assessment checklist

So the proper tools are essential to stay compliant, manage mileage reimbursements accurately, prevent inflated claims, and avoid wasting admin time. 

Can you use spreadsheets for grey fleet management?

We get it - we use them too. Spreadsheets are always there, easy to reach, and often the quickest way to get started. They’re fine at the beginning.

Use them to test whether you actually need a system, to understand what data drivers need to submit, what managers need to review, and maybe even to sketch out the basic structure of your process.

But they should stay a starting point.

As soon as you begin to scale - with more drivers, more journeys, and more people needing reimbursement - spreadsheets rarely hold up. Errors creep in, approvals slow down, versions multiply, and compliance risks increase.

That’s where spreadsheets stop helping and start holding you back. Grey fleet management needs more structure than a shared file can reliably provide.

Why grey fleet tools are different from traditional fleet systems

One thing we’ve learned from helping many UK teams implement Driversnote Teams is that responsibility for grey fleet management rarely sits in one place; it tends to be shared across the organisation rather than held by a single fleet manager.

In some organisations, mileage claims are approved by direct line managers, who then pass reports on to finance for payment through payroll. In others, a bookkeeper or finance team spot-checks routes and signs off claims centrally. Compliance and communication around HMRC rules might sit with HR, or with health and safety, or somewhere else entirely.

It often looks something like this:

• HR handles policy and employee communication
• Finance manages reimbursement and expenses
• Health & Safety oversees the duty of care
• Operations focuses on travel efficiency and productivity

Traditional fleet management systems are built for company-owned vehicles and centralised control. Grey fleet software needs to do the opposite: Adapt to a flexible organisation with shared ownership.

It needs to be easy for non-fleet specialists to use and minimise admin, regardless of who reviews, approves, or pays mileage claims.

What to look for in your grey fleet software? 

Privacy and UK GDPR

Privacy is a major concern when employees use their own vehicles for work. Most people are understandably uncomfortable with being tracked by GPS or telematics systems designed for company-owned cars.

A good grey fleet solution respects that boundary. Drivers should remain in control of their journey data, choosing which trips to submit for reimbursement while keeping private travel private. In practice, this means employees own their mileage log, and managers only see the business journeys that are actively reported.

From an organisation’s perspective, this approach supports compliance, auditability, and trust without collecting unnecessary personal data. From an employee perspective, it provides transparency, control, and reassurance that private driving isn’t being monitored.

UK GDPR compliance is a critical part of that balance. Mileage tracking software should store data securely, limit access appropriately, and follow privacy-by-design principles, ensuring personal data is protected while still giving organisations the visibility they need to operate compliantly.

Grey fleet tools should be scalable

Choose grey fleet software that can scale as your organisation grows. Over time, you may have more drivers or a more complex fleet, with a mix of personal vehicles, company cars, pool cars, and rentals. 

Flexibility matters

Your mileage solution should scale easily, support multiple vehicle types, and avoid forcing teams to manage separate systems.

How to scale your grey fleet: What breaks at 10, 25 and 50+ drivers

One system as your fleet evolves

As a UK organisation, you may start by reimbursing business mileage in personal vehicles at HMRC-approved rates. 

As the business grows, some employees might transition to company cars. With Driversnote, personal-vehicle drivers can continue to log mileage for reimbursement, while company-car drivers can use the same system to separate business and private use. You can still get the data you need for business-use calculations and a single, auditable mileage record across the mixed fleet.

Hire cars still need tracking

Short-term rentals aren’t reimbursed using standard mileage rates, but tracking is still essential. Mileage logs help verify fuel claims, enforce travel policy, monitor excessive driving, and demonstrate that the rental was used for business purposes only, reducing tax and compliance risk.

HMRC compliance: Why mileage documentation matters

In the UK, mileage tracking isn’t just admin; it’s a tax compliance requirement.

Mileage reimbursements are only tax-free if they follow HMRC rules and are supported by proper records. That means logging key journey details such as:

• Date and purpose of travel
• Start and end locations
• Total distance travelled

Without consistent records, claims can be difficult to justify during an HMRC audit.

Mileage software that produces standardised, audit-ready logs helps demonstrate that reimbursements are legitimate, policy-based, and compliant.

Also read: HMRC mileage requirements 

Mileage tracking beyond reimbursement

Accurate tracking reduces manual entry and helps prevent inflated or incorrect claims. It improves cost visibility and contributes to duty of care by documenting that driving activity is being managed responsibly.

Automatic mileage tracking keeps mileage logs accurate, while manually added trips are clearly flagged and displayed on a map. This makes it easy to verify routes, resolve disputes quickly, and catch inflated mileage before it impacts your budget, all while maintaining clear, audit-ready records.

In short: What to look for in grey fleet mileage software?

Grey fleet management software doesn’t mean you have to invest in an enterprise fleet platform. It does, however, require the right fundamentals:

• HMRC-compliant mileage logs
• Accurate, automated distance tracking
• A simple experience for everyday drivers
• Support for mixed fleets
• Clear business vs. private use separation
• Centralised reporting and audit trails
• Lightweight administration for shared ownership

Done well, mileage tracking for grey fleets makes business driving simpler, safer, and more accountable for everyone involved.

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