Read Your Invoice

The basic structure

Each service you own generates its own line item on the invoice covering the period being billed, plus a separate line for any promotional discount applied, shown as a negative amount rather than baked silently into the price. Tax, where applicable, is calculated on the subtotal after discounts.

Why a renewal total can look different from the first invoice

A "first month 50% off" style promotion only applies to that first invoice, the renewal after it bills at full price, and correctly shows a higher total, that is not an error or a price increase, it is the promotion ending as designed. A "20% off every renewal" style promotion instead shows the same discount line on every future invoice too, if you are unsure which kind applies to your order, the discount line item name usually says which.

Prorated charges

Upgrading a service mid-cycle generates a prorated charge, the difference between your old and new plan for the remaining days in the current billing period, rather than charging the new plan's full price again. This shows as its own line item distinct from the regular renewal.

Currency

An invoice is issued in whatever currency your account is set to at the time it is generated. Changing your account currency afterward does not retroactively change invoices already issued, only new ones going forward.

Before assuming an invoice total is wrong, check for a discount line that expired and a proration line from a recent upgrade, together they explain the overwhelming majority of "why is this different from last time" questions.