Teams running ads on several platforms almost always hit the same problem: finance's spend, the platform back office's spend and the BI report's spend disagree. The gap is usually not in the data but in the definitions.
First, currency. Ad accounts may bill in local currency while reporting is in USD or CNY. Which day's rate, and whether you use the platform's conversion or your own finance rate, can move the total by several percent. Store the original amount, the rate and the converted amount together so any layer can be traced.
Second, time zone. Platforms split days by account time zone, so across accounts in different regions the same 'today' is not the same window. Re-splitting on one business time zone is more accurate than adding up each platform's daily report.
Third, attribution window. Spend itself is unaffected, but the moment you compare spend against conversions and revenue for ROI, each platform's attribution setting has to be stated or the comparison is meaningless.
Settle all three during integration and most later reporting disputes disappear.