Read the statement structure
BillDiff organizes the provider, dates, total due, recurring charges, equipment, discounts, credits, fees, one-time items, and billing notices found in supported statements.
Normalize comparable bill items
Printed line items are mapped into stable categories so the same kind of charge can be compared across consecutive statements even when presentation or wording changes.
Reconcile the current bill
Deterministic arithmetic checks the signed line-item amounts against the printed statement total. BillDiff surfaces reconciliation problems instead of silently forcing the numbers to match.
Calculate what changed
Previous and current totals are compared cent-for-cent. Changed recurring items, removed discounts, new charges, credits, and one-time items are separated so a temporary spike is not automatically treated as a permanent monthly increase.
Only forecast explicit dated changes
A future event requires direct statement evidence such as a promotion end date, installment end date, or a notice with an effective date and amount. BillDiff does not invent a future date because a provider commonly changes prices.
Keep provider policy separate from bill evidence
Provider guides use first-party references to explain common billing mechanics. Those references provide context, but the result for a specific customer is based on that customer's uploaded statements.