The Integrated Customs Management System, the platform every import and export declaration in Ghana passes through. Often still called UNIPASS, after the consortium that built it.
It handles the declaration, the classification, the valuation, the permits from other regulators, the assessment and the payment, and it issues the release.
You will almost certainly meet it through a clearing agent rather than directly. That does not mean you should not ask to see your own declaration - it is where the values that produced your bill are recorded.