diff --git a/request.go b/request.go
index bcb10f1..1daa1ee 100644
--- a/request.go
+++ b/request.go
@@ -177,9 +177,9 @@ type Callbacks struct {
 
 // Expiry : Represent transaction expiry time
 type Expiry struct {
-	StartAt  time.Time `json:"start_at,omitempty"`
-	Unit     string    `json:"unit,omitempty"`
-	Duration int64     `json:"duration,omitempty"`
+	StartAt  *time.Time `json:"start_at,omitempty"`
+	Unit     string     `json:"unit,omitempty"`
+	Duration int64      `json:"duration,omitempty"`
 }
 
 // ChargeReq : Represent Charge request payload