Fleet mileage tracking: the indicators that cut lease excess mileage charges and grey fleet costs

Fleet mileage tracking means knowing, every month and for every vehicle, how many miles it has covered against its lease band, how many of them were business miles, and what each mile costs. Done monthly, it turns end-of-contract excess mileage charges into decisions you take a year earlier: re-banding, swapping cars between drivers or adjusting replacement dates.

This guide sets out the indicators that matter, a worked example in pounds on 50 leased cars, the ways to capture mileage (from driver declarations to connected-car data), what the split between business and private miles changes for tax, and how to manage the grey fleet. Voltaback, for example, reads mileage directly from the car with no box fitted and no location shared with the employer.

Why track fleet mileage?

Contract hire: paying for miles you do not drive, or for those you drive too much

Most UK company cars are on contract hire with a mileage band: for example 48 months and 80,000 miles. The rental is priced on that band. Two things can go wrong:

• The car runs over its band. At the end of the contract, the lessor charges every excess mile at the rate in the contract schedule. Wessex Fleet's analysis of nearly 700 contracts found that 24 % of company car drivers were on course to exceed their limits, with an average excess charge of £8,981 per car at the end of term, and an average excess rate of 32p per mile across its portfolio.
• The car runs well under its band. You have paid in the rental for depreciation that never happened. Many contracts refund unused miles at a lower rate than they charge excess miles, or not at all.

Both are invisible without tracking, because the bill arrives when the car goes back.

Source: Excess mileage charges in the UK, Wessex Fleet.

Matching cars to drivers

Within the same fleet, some drivers do 30,000 miles a year and others 6,000. Tracking shows early which cars will overshoot and which will undershoot, so you can swap them between drivers with similar needs before the gap becomes a charge.

Maintaining at the right time

Service intervals, tyre wear and brake checks depend on miles. Monthly mileage lets you plan servicing before the warning light, instead of after a breakdown. The guide to maintenance alerts covers what to set up.

Tax, insurance, carbon reporting and duty of care

• Tax: the business/private split drives mileage payments (advisory rates) and evidence for pool cars.
• Insurance: fleet policies are priced partly on exposure; accurate miles support renewals and claims.
• Carbon reporting: large companies report energy use and emissions, including company vehicles, under Streamlined Energy and Carbon Reporting.
• Duty of care: the Health and Safety Executive expects employers to manage work-related road risk, which starts with knowing who drives how much.

Source: Driving and riding safely for work, HSE.

Which indicators to track, and how often

Keep the dashboard short: four or five indicators reviewed every month beat twenty reviewed once a year.

Example of a trajectory calculation

A car on a 48-month, 80,000-mile contract has a pro-rata allowance of about 1,667 miles a month.

• After 14 months, it shows 29,400 miles. The pro-rata allowance at that point is 23,333 miles.
• It is 26 % ahead. At its average of 2,100 miles a month, it will reach about 100,800 miles at month 48.
• Projected excess: 20,800 miles. At an illustrative 12p a mile, that is about £2,500. At the 32p average Wessex Fleet observed, about £6,650.

Caught at month 14, you have 34 months to act. Caught at month 48, you have an invoice.

Always use the excess rate printed in your own contract schedule: it varies by vehicle, by lessor and by the original mileage band.

What to do when a vehicle drifts from its band

Four levers, from the cheapest to the most disruptive:

1. Swap cars between drivers. Give the high-mileage car to a low-mileage driver with a similar role, and the other way round. Both contracts drift back towards their bands at no cost, as long as the cars suit both drivers and the policy allows it.
2. Re-band the contract mid-term. Most lessors will re-write the mileage band during the contract. The monthly rental goes up, but the extra miles are priced at the rental rate, usually far cheaper than the excess rate at the end. Ask early: a re-band at month 14 spreads the cost over 34 months.
3. Change the replacement date. Extending a low-mileage contract, or ending a high-mileage one early and replacing the car, can be cheaper than running it to the end. Compare the early termination charge with the projected excess.
4. Change the driver's pattern. Sometimes the mileage is not needed: private use beyond the policy, long commutes that a pool car or train would serve better, or trips that could be grouped. A factual conversation, with the numbers, is usually enough.

For the tax side of leased electric cars, see the guide to leasing electric company cars.

Setting the right band at order

The cheapest excess mile is the one you never contract. When a car is replaced, set the new band from the driver's measured mileage over the last 12 months, not from the previous band or a fleet-wide default. Add a margin for known changes (new territory, new role), and record the assumption. A fleet that sets bands from real data typically sees far fewer re-bands in the following cycle.

How to capture fleet mileage

Driver declarations

Cheap and universal, but in practice someone spends the first week of every month chasing readings, and the figures often end in zero. They also give no evidence beyond the driver's word if HMRC asks.

Fuel and charge cards

Useful for petrol and diesel cars, where the driver types the odometer at every fill-up. For electric cars charged at home, there is no fill-up, so the reading disappears: one of the reasons EV fleets lose sight of mileage.

Phone apps

Mileage apps are popular with grey fleet and small businesses. They produce good HMRC-ready logs when used every day, but depend on the driver remembering to run the app and classify each trip.

Fitted telematics

A box wired into the car gives accurate trips and is the long-standing standard for vans. For company cars, it adds installation and removal at each car change, and it collects detailed location data, which needs strong justification under UK GDPR when the car is also used privately. The guide to vehicle tracking for business covers the legal framework.

Connected-car data

Most recent cars report their odometer, energy use and charging sessions to the manufacturer's cloud. With the driver's consent, that data can be read directly, with nothing to fit. This is the route Voltaback uses: monthly and cumulative miles per car, consumption and maintenance indicators, for more than 48 brands, with no box. It suits company cars especially well, because the car changes but the method does not.

Choosing a mileage tracking tool: a checklist

• Coverage: does it work for every make in your fleet, including electric cars that never visit a fuel pump?
• Effort for drivers: one-time consent, or a daily action?
• Data collected: miles only, or also location? Can private journeys be hidden from the employer?
• Car changes: does it follow the driver to the next car without new hardware?
• Outputs: monthly mileage per vehicle against the band, an HMRC-ready business mileage record where needed, and an export your fleet and payroll teams can use.
• Security: certification such as ISO 27001, and UK GDPR documentation you can show to drivers and employee representatives.

Tracking miles does not mean tracking journeys

For lease management, maintenance and cost per mile, you need miles, not routes. Collecting the position of a car used privately is intrusive and, under UK GDPR, requires a clear purpose, proportionality and transparency with drivers. The Information Commissioner's Office guidance on monitoring workers points the same way: collect the minimum necessary and tell people what you collect.

With Voltaback, the employer never receives the car's location. It receives miles, energy and alerts. If a business mileage log is needed for HMRC, it can be built without exposing private journeys to the employer.

Business and private miles: why the split matters

The UK benefit in kind on a company car does not depend on mileage: it is a percentage of the list price. But the split between business and private miles still drives several costs.

• Mileage payments: when a company car driver pays for the energy, the employer reimburses business miles at HMRC's advisory rates, 7p a mile for home charging and 15p for public charging for electric cars, from 1 September 2026. Petrol, diesel and hybrid cars use the advisory fuel rates by engine size. Only business miles qualify.
• Fuel for petrol, diesel and hybrid cars: if the employer pays for private fuel, the car fuel benefit charge applies unless the driver repays all private fuel. Repayments are usually calculated at the advisory fuel rate per private mile.
• Pool cars: a pool car avoids the benefit in kind only if private use is merely incidental and the car is not normally kept overnight at an employee's home. Mileage records are the evidence.
• Commuting: travel between home and a permanent workplace is private, a frequent source of over-claimed business miles.

For electric company cars, the split matters less if the employer repays the actual cost of electricity, since HMRC allows that tax free for business and private miles alike (EIM23900). The guide to company car mileage logs explains what HMRC expects in a log.

Sources: Advisory fuel rates, HMRC, EIM23900, HMRC.

Salary sacrifice cars

Salary sacrifice cars are leased with a mileage band too, and the excess charge is often passed on to the employee under the scheme agreement, or absorbed by the employer. Either way, an employee who discovers a £3,000 excess charge when the car goes back is an unhappy one. Monthly tracking lets you warn drivers early and re-band if needed.

Electric fleets: mileage, energy and charging together

Electric cars change mileage tracking in two ways. First, the fuel card no longer captures odometer readings, so fleets that relied on it lose visibility when they switch. Second, for an EV, mileage and energy belong together: kWh per mile is the efficiency indicator, and home charging is often repaid to the driver.

Three indicators are worth adding for electric and plug-in hybrid cars:

• kWh per mile per car, compared with the model's average. A car using 20 % more than its siblings points to driving style, tyres or a fault, which eco-driving coaching helps address.
• Share of charging at home vs public: public rapid charging can cost three times as much per mile as home charging.
• Plug-in hybrids' electric share: a PHEV that is never charged runs on petrol at a higher cost and higher emissions than its official figures. Monthly charging data shows which ones.

When the same tool reads mileage, energy and charging sessions from the car, a single monthly export can feed lease management and home charging reimbursement at once, instead of two suppliers and two processes.

Pool cars and shared vehicles

Pool cars need mileage per booking or per driver, not just per car, both for tax (private use must be merely incidental) and for accountability on damage and fines. A booking system plus the car's odometer at each handover is usually enough. Keep the records: they are the evidence that the car qualifies as a pool car.

The grey fleet: the miles you do not see

The grey fleet is employees using their own cars for work. It is often the least controlled part of a company's mileage.

What it costs

• AMAP: an employer can pay up to 55p per business mile for the first 10,000 miles in 2026 to 2027, then 25p, tax and NIC free. The 55p rate rose from 45p this tax year, so the same miles now cost about 22 % more.
• Scale: a 2016 study by the Energy Saving Trust for the BVRLA estimated about 14 million grey fleet drivers covering around 12 billion business miles a year, at a cost of more than £5.5 billion in mileage claims, in cars with an average age of 8.2 years. The figures are dated, but the order of magnitude explains why fleets look at it.

At 55p a mile, a grey fleet driver covering 12,000 business miles costs £6,000 a year in allowances alone (10,000 x 55p + 2,000 x 25p). For high-mileage employees, a company EV with its electricity repaid at cost is often cheaper.

Sources: Travel, mileage and fuel rates and allowances, HMRC, Grey fleet costing business billions, Fleet News.

Duty of care checks

An employer has the same duty of care for an employee driving their own car on business as for a company car driver. Minimum checks, at least once a year:

• Driving licence: valid, right categories, penalty points, using the DVLA's online service and a check code from the driver.
• MOT: current for cars over three years old.
• Insurance: covers business use, not only commuting.
• Vehicle condition: a simple declaration and, for high-mileage drivers, a check.

Source: View or share your driving licence information, gov.uk.

Controlling grey fleet mileage

• Require a journey-level claim: date, purpose, start and end, miles. Round-number claims should be queried.
• Compare claims with route distances for regular trips.
• Set a threshold above which a pool car, a hire car or a company car is required, for example above a few thousand business miles a year.
• Remember the commute rule: home to a permanent workplace is not business mileage.

What mileage tracking saves: a worked example on 50 cars

Assumptions, which you can replace with your own:

• 50 company cars on contract hire, 48 months and 80,000 miles each (20,000 a year).
• In line with the share observed by Wessex Fleet, 12 cars (24 %) run about 25 % above their band, so about 100,000 miles at the end of term. Another 10 cars run about 25 % below.
• Excess mileage rate in the contract: 12p per mile (illustrative; check your schedule).
• Re-band rate: excess miles priced into the rental at about half the excess rate.

Without tracking: the bill arrives at the end of term

• 12 cars x 20,000 excess miles = 240,000 miles.
• At 12p, £28,800 in excess charges. At the 32p average Wessex observed, £76,800.
• The 10 under-used cars return about 200,000 unused miles, largely paid for in the rentals and rarely refunded in full.

With monthly tracking: swaps and re-bands at month 14 to 18

• Swaps: 8 of the 12 over-running cars are matched with 8 of the 10 under-running cars in similar roles. Over the remaining term, both groups drift back towards their bands. Excess on those 8 cars falls close to zero.
• Re-bands: the 4 remaining over-running cars are re-banded at month 14. Their 80,000 extra miles are priced at about 6p in the rental instead of 12p: about £4,800 instead of £9,600.
• Result: at 12p, excess and re-band costs fall from £28,800 to about £4,800, a saving of about £24,000 over the contract. At 32p, the saving is several times larger.

Sensitivity: how much is at stake on your fleet

The higher the excess rate in your schedule, the more monthly tracking is worth. Larger SUVs and premium cars usually carry the highest rates.

The time saved by the fleet manager

Chasing 50 odometer readings every month, checking them and entering them takes about 10 minutes per driver, counting reminders: roughly 100 hours a year. Automatic capture brings that close to zero, and the readings are reliable enough to act on.

The business mileage payments

With measured business miles, mileage payments are paid on actual miles instead of declared ones. Over-claiming by a few per cent on a fleet of this size is common and adds up to thousands of pounds a year, which the telematics savings simulator lets you estimate for your own fleet.

What the driver gains

Tracking is easier to roll out when drivers see what is in it for them:

• No more monthly reading to photograph and send.
• No surprise at the end of the lease, especially for salary sacrifice cars where the excess may be recharged.
• Correct, on-time mileage payments, without filling in a log every evening.
• Maintenance reminders before a warning light.
• Privacy: miles and alerts, not positions.

Setting up fleet mileage tracking in five steps

1. Gather the contracts

List every vehicle with its lessor, contract start date, term, mileage band, excess rate and refund rate for unused miles. This is often spread across several lessors' portals; a single sheet is the starting point.

2. Set a single reading date

The same day every month for all vehicles, for example the last working day. It makes trajectories comparable and gives payroll a fixed cut-off for mileage payments.

3. Automate capture where you can

Connected-car data for recent cars, telematics where a box is already fitted, charge or fuel card readings as a fallback, and declarations only for the remaining vehicles. Tell drivers clearly what is collected and why.

4. Connect the data to your fleet tool

Mileage is useful only once it sits next to the contract data: band, pro-rata allowance, forecast, excess cost. Whatever tool you use, the monthly reading must update these figures without manual re-keying.

5. Hold a quarterly review

Every quarter, review the cars more than 10 % ahead or behind their band, decide swaps and re-bands, and check grey fleet claims against thresholds. Fifteen minutes per quarter on a well-built dashboard is enough for a 50-car fleet.

Who does what

Mileage tracking touches three teams, and it works best when each knows its part:

• Fleet manager: owns the contract data, the monthly dashboard, swaps, re-bands and replacement bands.
• Finance and payroll: own mileage payments, AMAP for the grey fleet, the tax evidence and the budget impact of re-bands.
• HR: owns the car policy, the grey fleet threshold, driver communication and the data protection notice.

A one-page monthly report shared by all three keeps decisions fast:

1. Cars more than 10 % ahead of their band, with projected excess in £.
2. Cars more than 10 % behind, available for swaps.
3. Decisions taken last month and their effect.
4. Grey fleet miles and cost, against threshold.
5. Cars due a service within 1,000 miles.

The same report, summarised each quarter, gives leadership the cost per mile trend and the savings achieved, which is usually what keeps the project funded.

Common mistakes

• Looking at mileage once a year, or only at the end of the contract.
• Using total miles instead of pro-rata miles: a car with 30,000 miles is fine at month 20 and a problem at month 12.
• Forgetting electric cars: no fuel card, no odometer reading at the pump.
• Collecting locations "just in case": it creates UK GDPR exposure without helping lease management.
• Ignoring under-used cars: they are a lever for the over-used ones.
• Treating the grey fleet as a payroll issue only: it is also a duty of care and cost issue.
• Setting replacement bands from the old contract instead of the driver's measured mileage.
• Letting swaps happen informally, without updating the contract records and the insurance.

What it changes in practice

Monthly mileage tracking is one of the few fleet projects that pays for itself within the first contract cycle: it prevents excess charges, makes mileage payments accurate and frees the fleet manager from chasing readings. The mileage line is also a large part of the total cost of ownership of a fleet, together with energy and tax.

Start with the cars that already report their mileage on their own, measure for three months, and let the first re-band or swap make the case for the rest of the fleet. Three monthly readings are enough to draw a reliable trajectory for each car and to see which contracts deserve a call to the lessor.

Switch to automatic mileage tracking

Your cars already know their mileage. The job is to read it every month, without chasing drivers and without collecting more than you need.

Voltaback reads miles, consumption and maintenance indicators from the car, with no box and no location shared with the company, for more than 48 brands. Discover our telematics without a box or talk to our telematics team about your fleet.