A £50 top-up can feel like a charging cost on the day you pay it. It is not necessarily the cost of the electricity your car has used that day. To track prepaid charging credit properly, separate the money added to an account from the credit consumed at each charging session. That distinction is what turns a rough wallet balance into an honest record of what your car actually costs to run.
Prepaid credit is useful. It can make public charging quicker, avoid repeated card authorisations and help drivers manage a regular budget. But it also makes cost tracking easier to distort. If you record only the top-up, a single month’s figures may look expensive even when much of that balance will power miles driven later. If you record only sessions and ignore top-ups, you can lose sight of cash committed, remaining credit and receipts needed for VAT or expenses.
Why prepaid charging credit needs its own record
A prepaid charging balance sits between your bank account and your energy use. It is money paid in advance, not automatically a completed charging expense. The actual cost becomes clearer when credit is used for a session and the operator confirms the kWh, rate, time-based charges and any fees.
That matters most when your driving varies. A driver who tops up before a long holiday, then charges over several weeks, should not assign the whole amount to the first journey. Likewise, a self-employed driver may need to show when money was paid, how much VAT was charged and which business journeys consumed the energy. One entry cannot reliably do all three jobs.
A useful record has two connected parts: the prepaid block itself and the charging sessions drawn from it. The block tells you the opening amount, top-up date, payment method, receipt total and any VAT. Each session tells you what was consumed, when, where, how many kWh were delivered and the final amount deducted. Together, they show both your cash position and your running cost.
Record the top-up without treating it as a full charging session
When you add credit, log it as a prepaid energy block. Capture the gross amount paid, any bonus credit, the provider, the date, the receipt reference and the balance after the top-up where available. If the receipt shows VAT, retain the net amount and VAT separately rather than trying to rebuild it from memory later.
The distinction between money paid and usable credit is worth making. Some networks offer promotional credit, while others apply a set-up charge or fee. A £50 card payment may produce £50 of spendable credit, but it may also produce a different balance if a fee, discount or bonus applies. Your ledger should reflect what actually happened, not what you expected to happen at the charger.
For personal budgeting, the gross payment is normally the useful cash figure. For VAT-registered business use, keep the underlying VAT evidence and apply your own accountant’s guidance on what can be reclaimed. A charging-app statement alone may not contain the information required for every situation, particularly where the network is acting as an intermediary.
Do not force an exact pence-per-kWh figure onto the top-up itself. Until the credit is spent, you may not know the mix of chargers, tariffs and idle fees it will cover. Treating the block as a fixed electricity rate can produce a tidy-looking number that is simply wrong.
Watch for expiry, fees and unusable balances
Prepaid credit is not always equivalent to cash. Check whether the operator sets an expiry date, minimum balance rules, account closure terms or charges that may consume credit without adding energy to the battery. A small stranded balance is still a vehicle expense if it cannot reasonably be recovered or used.
Record an expiry date where one exists. It gives you a practical prompt to use the balance or make a deliberate decision to write it off. That is better than discovering months later that your charging history looks cheaper only because part of the cost disappeared from the records.
Track prepaid charging credit as sessions happen
At the charger, record the session against the relevant prepaid block or provider balance. In real conditions, this must be quick enough to do one-handed, in the dark, while you are trying to get back on the road. Start with the details that are hardest to recover later: date, location, kWh, amount deducted and the vehicle mileage.
The final receipt or app screen should settle the entry. Public charging prices can include energy charges, connection fees, parking, overstay charges or a tariff that changes by time of day. Record the total actually deducted, then preserve a clear breakdown when available. This lets you see the true public-charging cost without pretending every pound went into the battery.
If the network only shows a balance reduction and no session total, record the before-and-after balance and flag the session for checking. Do not invent a rate from the nearest charger tariff. The final cost may differ because of membership pricing, roaming charges or a fee applied after unplugging.
It also helps to distinguish between three practical measures:
- cash paid into credit during the period;
- charging credit consumed during the period; and
- energy delivered to the vehicle during the period.
These figures answer different questions. Cash paid helps with bank budgeting. Credit consumed is the better basis for monthly operating costs. Delivered kWh helps you assess charging efficiency and compare sites or tariffs.
Use the consumed value for cost-per-mile reporting
For a meaningful cost-per-mile figure, match the cost of charging credit consumed to the miles driven over the same reporting period. If £32.40 of prepaid credit was used in April and the car covered 1,080 miles, the public-charging component was 3p per mile before adding home energy, maintenance, insurance, tyres and other running costs.
That does not mean every April mile was powered solely by those sessions. Batteries carry energy between days, and most EVs are charged from more than one source. The aim is not false precision at individual-trip level. It is a consistent, auditable monthly or quarterly view built from real receipts and recorded mileage.
If you charge at home as well, keep home charging separate from prepaid public credit. Home electricity may be calculated from a smart tariff, a fixed unit rate or a blended household rate. Public credit should retain its own session costs. Combining them too early hides the difference between the charging choices you control and the ones made necessary by a journey.
A platform such as Amperlo can hold prepaid blocks, charge entries, mileage and receipts in one mobile record, then calculate energy-only and wider ownership costs from the entries you have actually logged. The useful outcome is not a promotional saving figure. It is an evidence-based view of what your car actually costs to run.
Reconcile the balance before it becomes a problem
Once a month, compare the app’s displayed prepaid balance with your own record. Start with the previous closing balance, add new credit and subtract session deductions, refunds and any fees. The result should broadly match the provider balance. If it does not, investigate while receipts and session screens are still available.
Small differences can be legitimate. A session may be pending, a deposit may be released later, or a network may post an overstay fee after the energy charge. Large or persistent differences usually point to a missed session, an incorrectly entered top-up, a currency conversion issue when travelling, or a fee that was never recorded.
This monthly check also protects business records. It is much easier to correct one missing £7.80 session in the week it happened than to rebuild a year’s public charging from bank statements. Bank statements prove money left your account. They rarely prove the kWh, VAT treatment or vehicle use behind it.
The best prepaid-credit record is not the most complicated one. It is the one you can maintain at the charger and trust when you review your costs later. Log the top-up, capture each deduction, keep the receipt and reconcile the balance. Then the number beside your cost per mile has a source, rather than a sales pitch.
