the G/L account to which the value will be posted is chosen from the General Posting Setup and for the VAT part from VAT Posting Setup.
On the Vendor card You have the Gen. Bus. Posting Group and VAT Bus. Posting Group.
On the item card You have the Gen. Prod. Posting group and VAT Prod. Posting group.
Based on these two combinations from the Posting Setup tables the G/L account for Purchases is chosen. So if You need a specific account, that only these kind of transactions are posted there, then You might have to create a new Gen. Prod. Posting group (and maybe VAT Prod. Posting group if needed), and assign it to Item card, then also create a new line in General Posting Setup with the combination of Gen. Bus. Posting group (that is used on this Vendor) and the new Gen. Prod. Posting group - and provide the needed G/L account in the Purchase Account column.
You can always verify if the G/L will be correct before posting by doing the Posting Preview.
