How overdelivery works
A daily budget is a target, not a shutter. On days when there is more qualifying demand — a search spike, a payday, a festival week, a competitor pausing — delivery can push above the daily figure, and on slower days it falls below. Across a billing period the two are meant to balance out.
Two things bound it. The charge for a billing period is capped at the daily budget multiplied by the typical number of days in a month, and if the charge for a period exceeds that limit, Google credits the difference. So a single alarming day is normally arithmetic rather than a fault, and the place to check is the billing summary for the period rather than the cost column for yesterday.
Why overdelivery matters
Mostly it matters because of how it looks. A client or a finance team watching daily spend sees a figure above the agreed number and reasonably asks what went wrong, and the answer — that it will even out — is unconvincing without the monthly limit explained in advance.
It matters practically for cash flow. Small accounts, and accounts paying with cards that carry modest international limits, feel a heavy day sooner than a large advertiser does, because the account reaches its billing threshold and charges earlier than expected. That is a real constraint for businesses in Nepal running international campaigns, and it is worth planning around rather than discovering.
Where it causes trouble
Changing a budget partway through a period is the biggest source of confusion. The monthly limit is worked out from the budget in force, so an increase mid-period changes the arithmetic as well as the delivery, and the total for that period can come in higher than the sum you had in your head.
Forecasting from a single day is the other. One busy day extrapolated across a month produces a frightening number that will not happen. The same trap works in reverse after a quiet day, and both lead to budget changes that were never needed.
What to do about it
Judge spend across the billing period rather than the day, and say so to whoever reads the reports before the first heavy day arrives rather than afterwards. Note the date whenever you change a budget, so an unexpected total can be explained rather than argued about.
Where variance genuinely cannot be tolerated — a client cap, a card limit, a promotion with a fixed pot — set the daily figure below the level you can comfortably afford, or use a campaign budget with fixed dates so the entire amount is bounded. Both trade a little delivery for certainty, which is often the right trade when the money is not yours.