Manual controls On a monthly basis, VTTI’s stocks are reconciled and the (monthly) supplementary declaration (GPA) is sent to Customs.  A link to VTTI's "C&E - Customs monthly declaration GPA" procedure is included here . The specific modalities of GPA of VTTI Terminals II B.V. related to the nature of goods (liquid bulk) are captured in the Work agreement with the Customs authorities.  A link to "Work agreements GPA VTTI Terminals II BV" is included here . Besides the above controls. several other controls are included in BzCtrl.