How to catch a Google Ads or Meta overspend before your client does

Underperformance is arguable. The auction got expensive, the market moved, the landing page converts worse than it did in June. You can walk a client through it and still keep the account.

Overspend is not arguable. You agreed to a number, the number was exceeded, and your client is looking at a charge they did not approve. The damage is not to the campaign. It is to the assumption that you are watching.

Neither platform holds the number your contract uses

Your contract is written in monthly terms. Neither ad platform has a monthly budget.

Google Ads has an average daily budget, and Google publishes exactly what that permits:

Your daily spending limit (two times your average daily budget for most campaigns) on any particular day.

Your monthly spending limit (30.4 times your average daily budget for most campaigns) in any particular month.

30.4 is 365 divided by 12. So a €50 daily budget is not €1,500 a month. It is up to €1,520 over the month, and up to €100 on any single day. Both of those are inside the rules. Neither is a malfunction you can escalate.

Meta does not have a monthly budget either. It has daily budgets and lifetime budgets. If you promised a client a monthly figure, there is no field on either platform that holds you to it.

On Meta, nobody will tell you the ceiling

Google states its limits plainly, so you can compute the worst case. Meta is different, and the difference is worth seeing directly.

Search for how far Meta can exceed a daily budget and you will find confident answers that disagree with each other. One vendor states Meta "can spend up to 25% above daily budgets on high-opportunity days." Others put the figure at 75%. Neither cites Meta.

Meta's own help page on daily budgets is rendered by JavaScript, so it is not readable without a browser. That is not evidence of anything hidden. It is the reason the secondary sources drifted apart and never got corrected.

The practical consequence is the point: on Google you can calculate your exposure from published numbers. On Meta you cannot, so the only reliable figure is the spend that already happened.

What the platforms give you natively

Google Ads has automated rules, which "make automatic account changes based on chosen settings and conditions," and they can email you when a condition fires. That is a real safety net and it is free.

Its shape is the limitation. A rule lives inside the account it was created in. A book of client accounts means creating the rule in each one and maintaining it in each one, and a rule that was never added to the account you onboarded last month is not protecting anything.

Meta has account spending limits. That is a hard stop rather than a warning. When it trips, delivery stops. It protects the invoice and it takes the campaign down with it, and you find out after the fact.

Neither mechanism watches pace against a monthly commitment, because neither platform has a monthly commitment to watch.

What actually catches the drift

The thing worth alerting on is not spend. It is the gap between the spend you have and the spend you should have by now.

expected  = monthly budget / days in month * days elapsed
variance  = actual spend - expected

A client on €3,000 for the month, twelve days in, should be around €1,200. At €1,700 they are 42 per cent ahead of pace with eighteen days to go. Nothing has broken a platform rule. The month is going to end roughly €1,250 over the number you agreed, and the only reason to know that today rather than on the invoice is that somebody was computing it.

The budget pacing calculator runs the same arithmetic for one client, with the formula shown and the month set to 30.4 days.

Two honest notes on that arithmetic, because pacing models hide their assumptions and then surprise you.

Adswave and the calculator normalise to a 30.4 day month rather than the calendar month, matching the constant Google publishes. That is deliberate. In the calculator's projection it reads slightly low in a 31 day month and noticeably high in February. In Adswave's pacing view, a client spending evenly shows about -1.9 per cent in a 31 day month and about +8.6 per cent in February.

Counting today as a whole day while today's spend is still partial reads as underspend until the day is over. Adswave's pacing windows all end today, so the shortest windows lean the most.

A budget threshold on its own is not enough

The tempting version of this is a percentage alert. Tell me when the client hits 75 per cent of budget. That is better than nothing and it is genuinely late.

A threshold tells you the total is high. It does not tell you why, and the why is what you need to act. A cost per click that tripled overnight shows up in cost per click hours before it shows up as a budget percentage, and by the time the percentage moves you have already bought the expensive clicks.

Shape.io was the pacing tool this category was built around, and it documented this exact limit in its own help centre:

Shape currently does not support custom alerts based on features such as campaign impression thresholds.

That sentence is a vendor writing down a capability it did not have, which means customers asked for it enough to warrant an article. Shape is no longer purchasable, so the answer that ranks for the question is now a limitation of a product you cannot buy.

The number you are alerting on is still moving

This is the caveat most tooling content omits, including content written by people selling the tooling.

Reported ad spend settles after the fact. A figure you read at nine in the morning can be revised later, which means a fast alert is sitting on top of a number that is not final. Adswave evaluates alerts hourly, so this applies to Adswave.

Treat an alert as a reason to open the account, not as a settled fact. And do not reconcile a client invoice against a mid month figure from any third party tool, including this one. Reconcile against the platform's own billing.

Saying so costs nothing. Finding out from a client that the number you sent them moved costs the relationship, which is the thing this whole article is about.

What Adswave does about it

Adswave connects Google Ads and Meta, computes expected against actual spend per client, and alerts on the variance rather than on a raw threshold.

Alerts cover nine metrics, impressions, clicks, cost, conversions, conversion value, click through rate, cost per click, return on ad spend and cost per conversion, plus pacing variance itself. Directions are up, down or either. Windows are 1, 7, 14 and 30 complete days ending yesterday. Rules are checked hourly.

Two things worth stating plainly.

Alerts are on every plan, including the €19.99 tier. They are not held back for a higher one. Alert emails go to the organisation's owners and admins, everyone sees alerts in the app, and seats are unlimited on every plan, so adding the whole team does not change the bill.

Adswave is read-only. It requests Meta's ads_read permission and never ads_management, and on Google it calls read endpoints only. The security page lists exactly which. It will tell you a client is running 42 per cent ahead of pace. It cannot pause the campaign for you, and it will not. You go into the platform and make the call yourself.

Questions people ask

How much can Google Ads actually overspend my daily budget?

Google publishes both limits. Up to two times your average daily budget on a single day, and up to 30.4 times it across a month. Spending inside those bounds is the system working as documented.

Does Meta stick to the daily budget I set?

Not on a given day. Meta optimises delivery across days, so individual days run above and below the figure you set. Published third party estimates of the daily ceiling disagree with each other and none of them cite Meta, so treat any specific percentage you read with suspicion, including the ones above.

Can I just set up alerts inside Google Ads?

Yes, with automated rules, and you should. The gap is that the rule lives in one account. Across a book of clients you are maintaining it per account, and the account you onboarded most recently is the one where it is missing.

What is a reasonable pacing variance to worry about?

It depends on how much month is left. Ten per cent ahead on day three is noise. Ten per cent ahead on day twenty five is roughly the final number. Adswave's pacing alerts use the same threshold on the 3rd as on the 25th, so read an alert with the date in mind.

Why alert on metrics and not just on budget?

Because the budget percentage is the last thing to move. Cost per click, cost per conversion and click through rate change first, and they tell you what to fix rather than just that something needs fixing.

Adswave watches Google Ads and Meta budgets for agencies pacing 5 to 35 clients. Read-only, alerts on every tier, branded client reports in 12 languages. Start a free trial, no card required.

Google budget limits quoted from Google Ads Help, checked 3 September 2026. Shape.io help centre wording checked the same day. Meta's own daily budget documentation could not be read without a browser, which is stated above rather than worked around.