The key point is that Amazon backdates ad sales, but it does not backdate actual sales totals.
Here’s how it works:
When you spend money on ads today, Amazon immediately records the ad spend for today.
However, ad sales are attributed retroactively for up to 14 days after the click.
So what happens is this:
• Today’s real sales might be $100
• Over the next 14 days, Amazon may determine that $1,000 of sales were actually caused by today’s ads
• Amazon then backdates those ad sales to today
Now look at the metrics:
ACoS = Ad Spend ÷ Ad Sales
This uses the backdated ad sales, so it might be $50 ÷ $1,000 = 5%
TACoS = Ad Spend ÷ Total Sales
This uses only the actual sales that happened that day, which were $100
So TACoS = $50 ÷ $100 = 50%
That’s why TACoS can appear higher than ACoS.
Nothing is wrong with the math. The difference exists because:
• Ad sales are updated retroactively
• Total sales are fixed to the day they occurred