No, the idea of the declared amount is that you pay taxes on it, not that you pay it in full. So if you declare at $20 (and it's accepted) and there's a 10% VAT, that means you only have to pay $2.
The declared amount is what's written on the merchant's invoice, which is what's used for the customs declaratio.
added: 6/26/2023 , modified: 7/21/2023