Sellerboard fees

I’m a VAT-registered seller on Amazon Uk and have been comparing my profit margins between Sellerboard and SellerAmp. I’ve noticed a significant difference in the margins, which I suspect may be due to how VAT and Amazon fees are calculated on each platform. There are also discrepancies between the Amazon fees shown on SellerAmp and Sellerboard.

How does Sellerboard factor VAT into the cost of goods sold (COGS)? Should VAT be included or excluded when calculating COGS?

Additionally, I’m evaluating whether to stay on the standard VAT scheme or switch to the flat rate scheme. Could you provide guidance on how to calculate margins for both VAT schemes using Sellerboard? I’d like to make an informed decision about which scheme is more advantageous for my business.