Tracing a jump in fuel costs
How a transporter traces a sudden jump in its fuel bill through the general ledger: the month-on-month view, every line, budgets and duplicate bills.
By Achekam · · 4 min read · For Logistics businesses in South Africa, Nigeria, Kenya
The management accounts land on the owner's desk and one line jumps out: fuel. The fleet ran the same routes as last month, nobody added a truck, and yet the diesel bill is far higher. The owner's first thought is theft; the depot manager's is that the price went up; the bookkeeper quietly wonders whether something was posted twice.
Any of them could be right, and guessing is how the wrong person gets blamed. The answer is in the books, line by line. This article shows a transporter in South Africa, Nigeria or Kenya how to trace a fuel cost spike through the Achekam ledger, from the headline figure to the individual slip, before asking anyone a pointed question.
The income statement against the month before
Start where the problem showed up. Management accounts show an income statement for a chosen period beside the period before, both added up from the business's own journals and exportable as PDF or CSV.
Read three things together:
- Fuel against revenue. If freight revenue rose too, more loads may simply have burned more diesel. A spike in cost with flat revenue is the worrying case.
- Fuel against other running costs. If tyres and repairs also jumped, the fleet may have worked harder, or a new long route started.
- The month before that. Export a few months as CSV and look at the trend. A one-month spike and a steady climb have different causes.
Price is the first suspect to rule out. Fuel prices move with taxes and markets, and occasionally with a rate change: in Kenya, at the time of writing, VAT on premium petrol, illuminating kerosene and automotive diesel is charged at 8% from 15 April 2026 to 14 October 2026, and a temporary rate ending moves the pump price with it. Kenyan transporters should also note that supplier bills currently offer only 15% or 0% VAT and default to 15%, so check the VAT on every fuel bill line against the slip.
Every ledger line in the fuel account
If price does not explain it, open the detail. The general ledger lists every posted line, so open the fuel account for the month and read it from top to bottom.
Sort or scan for:
- Unusually large single lines. A bulk delivery to the yard tank, perhaps, which is a timing issue rather than extra consumption.
- Lines from an unfamiliar supplier or depot. Fuel bought somewhere new deserves a question.
- Lines dated outside the month's trips. A fill-up on a day the truck was in the workshop.
- Lines that are not fuel at all. An oil change, a car wash or a driver's meal posted to fuel.
- Repeated amounts on the same date. The classic sign of a duplicate.
The trial balance shows each account for all time, for a period or at a date, and says whether debits equal credits, which lets you check the fuel account's total for any date range against the depot's own statement.
Budget versus actual
A business can set a budget per account and period and compare it with actual figures from its ledger. If the fuel budget was set from planned kilometres or planned loads, the comparison tells you whether the month was expensive against plan, not just against last month.
A useful next step is a rough consumption check outside the system: take the month's loads and kilometres from your trip records and the fuel volume from the depot statements, and see whether litres per kilometre changed. A sharp change in consumption with no change in routes points to the trucks or the drivers; no change in consumption points back to price or to the books. Splitting fuel by truck makes this far easier, as described in running cost per truck.
Duplicates and misposted bills
Duplicates are common with fuel because the same purchase can arrive by several routes: a depot invoice, a fuel card statement, a driver's slip, and an e-mailed copy of the same invoice.
A business records supplier bills line by line with VAT, and a bill without a purchase order waits for approval before it posts. Supplier invoices and slips uploaded to Financial Intake become suggested postings; AI can suggest, but only a person approves and posts. Low-confidence fields and possible duplicates wait in the Intake Review Queue for a person. If the same depot invoice was uploaded to Financial Intake and also captured as a bill, approving both records the fuel twice; carrier invoices as suggested postings explains how to keep one route for each kind of document.
ICAEW's guide on how to identify and deal with fake invoices sets out warning signs such as invoices that do not match purchase orders and delivery records, and controls such as separating duties, which apply just as well to fuel bills that should not be there.
Questions to ask the depot
Only once the books are checked should the questions go out. By then they can be specific:
| Finding | Question |
|---|---|
| A large delivery to the yard tank | Was the tank filled, and what was the dip reading before and after? |
| Fill-ups at an unfamiliar station | Who authorised fuel there, and on which trip? |
| A truck filled on a non-trip day | Where was the truck, and who had the card? |
| Volumes above the tank's capacity | Which vehicle actually received the fuel? |
| A higher price per litre than the posted price | Has the supplier's rate or discount changed? |
Keep the tone factual. Most fuel spikes turn out to be timing, price or a posting error; a few are something worse, and the ledger will have shown you which lines to ask about.
After the investigation
Correct any posting errors with a reversal and the right entry, note what caused the spike, and add one control so it cannot recur unnoticed: a monthly comparison of depot statements with the fuel account is usually enough.
General guidance only, not advice on your own circumstances. Tax and payroll rules change: check the current position with the authority or your adviser.
