For the analysis of comparable metrics from all your ad services costs must result in a VAT-exclusive way.
The standard integration of Google AdWords reports cost data not including VAT.
- 10USD of campaign costs,
- 12USD charged including VAT,
- Google Analytics report shows total costs 10USD.
Specify the percentage of VAT in the pipeline settings (VAT rate in AdWords may be different from VAT rate in Facebook) to import a proportional amount of Facebook costs.
If you don't consider VAT while importing cost data, you'll end up overestimate the costs of non-Google campaign.
As a result, you wouldn't be able to make correct conclusions on the efficiency of a campaigns, e.g. redistribute the advertising budget in favor of campaign with lower ROAS.