Variable electricity contracts in Belgium often include indexation clauses. When the reference index changes, your unit price may be adjusted. This article explains how indexation works and how to validate it on your supplier invoice.
What is indexation?
Indexation links your energy price to a reference index (e.g. a commodity or consumer price index). When the index moves, your supplier adjusts your €/kWh or €/kW rate according to the formula in your contract. This keeps your price aligned with market or inflation movements.
What to check on the invoice
Invoice validation checklist
Reference index
Verify the applied index matches the one in your contract.
Index value date
Check that the index value is taken at the date specified in your contract.
Formula
Confirm the formula (e.g. base price × index / base index) is applied correctly.
Look for the indexation section on your invoice and run through the checklist above.
Common mistakes
Wrong index reference, wrong date for the index value, or a formula that does not match the contract. If you spot a discrepancy, document it and escalate with your supplier. Use our electricity bill audit checklist to verify indexation alongside other line items. electricity bill audit checklist.
Capacity tariff and indexation
The capacity tariff (€/kW) can also be subject to indexation. Check your contract for how capacity rates are adjusted. For a complete overview of the capacity tariff in Belgium, read our capacity tariff Belgium guide. capacity tariff Belgium guide.
Key takeaway
Indexation is a standard clause in variable contracts. Check each invoice: the reference index, the value at the relevant date, and the formula must match your contract. Document any discrepancy and escalate with your supplier. Use the electricity bill audit checklist to validate indexation alongside other line items.