Under-delivery

Under-delivery is when an ad campaign gets fewer impressions, reaches fewer people or spends less budget than was set or promised for the same period. Advertisers in Vietnam often describe it casually as “không tiêu hết tiền” (the budget isn’t spending) or “chiến dịch không lên” (the campaign won’t take off).

What is under-delivery?

The term covers two different situations:

• Reserved buying: you buy a set number of impressions or a set reach at a fixed price, such as Reach & Frequency on TikTok or a guaranteed line item in Google Ad Manager. Under-delivery means the actual result falls short of what was booked.
• Auction buying: you set a budget and the platform does the bidding. Under-delivery means the campaign spends well below its budget and therefore produces fewer results than planned.

One low-spend day is not necessarily under-delivery. Google Ads deliberately spreads spend across days. Some days come in below the average daily budget and some go above it, but spend never goes over 2 times the daily budget in a single day or 30.4 times the daily budget in a month (Google Ads Help, About average daily budgets, accessed October 2026). That is why pacing should be judged over the whole campaign period.

How to calculate delivery pacing

Pacing = (Actual results / Planned results) / (Days elapsed / Total days)

Hypothetical example: a campaign books 2,000,000 impressions over 10 days on a budget of VND 60 million. After 5 days it has delivered only 700,000, or 35% of the plan, while 50% of the time has gone by. Pacing is 35% / 50% = 70%. To hit the target, the last 5 days need 260,000 impressions a day, close to double the current 140,000 a day. If the CPM holds at VND 30,000, the campaign has spent only VND 21 million so far.

Common causes

• An audience that is too narrow or a flight that is too short. TikTok advises Reach & Frequency campaigns to avoid “very narrow” audiences, avoid short runs (one-day campaigns in particular) and avoid setting a reach rate of 80% or more, since all of these tend to under-deliver (TikTok Business Help Center, How to create Reach & Frequency campaigns, November 2025).
• Not enough inventory. Google Ad Manager names a shortage of available impressions as the main reason line items under-deliver, and it offers an “Expected to underdeliver” filter to catch the problem early (Google Ad Manager Help, Review the status of a line item, accessed October 2026).
• Price controls that are too tight. Meta’s Marketing API documentation states that cost cap and bid cap strategies may not spend the full budget once they hit their limits (Meta for Developers, Bid Strategy, accessed October 2026).
• Ads not yet approved, or restricted. TikTok Ads Manager uses statuses such as Pending (under review, not running yet) and Limited Delivery (delivering only partly) (TikTok, Ad statuses and definitions, June 2025).
• Scheduling and frequency. A narrow time window, or a low frequency cap on a small audience, leaves the system with nobody left to show the ad to.

How is under-delivery different from over-delivery?

Frequently asked questions

Are you charged for the part that did not deliver?

For auction campaigns, unspent budget is not charged. For reserved buys, how the shortfall is handled depends on each platform’s terms or your contract with the publisher, so read them closely before you book.

Should an awareness campaign use reserved or auction buying?

Reserved buying fits when you need to be sure of reaching enough people within a fixed window, such as a product launch. Auction buying is more flexible on budget. See also Reach objective and how to calculate reach and frequency.

If your campaigns often fail to spend their budget and you are not sure why, the Adtek team can review the settings with you. Reach us through our contact page.