diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9182acf..906c5d7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,5 @@
-v 1.0.1
+v 1.0.2
+  - sandbox: add support for optional case for new payments. #32
   - payment: missing PayAmount and PayCurrency fields. #30
 
 v 1.0.1
diff --git a/README.md b/README.md
index 28faaf6..801c5d9 100644
--- a/README.md
+++ b/README.md
@@ -33,7 +33,7 @@ Topic|Endpoint|Package.Method|Implemented
 ## Installation
 
 ```bash
-$ go get github.com/matm/go-nowpayments@v1.0.1
+$ go get github.com/matm/go-nowpayments@v1.0.2
 ```
 
 ## CLI Tool
diff --git a/cmd/np/main.go b/cmd/np/main.go
index a7ca83c..6f0fd7c 100644
--- a/cmd/np/main.go
+++ b/cmd/np/main.go
@@ -24,6 +24,7 @@ func main() {
 	showCurrencies := flag.Bool("c", false, "show list of selected currencies")
 	newInvoice := flag.Bool("i", false, "new invoice")
 	newPaymentFromInvoice := flag.String("pi", "", "new payment from invoice ID")
+	pcase := flag.String("case", "success", "payment's case (sandbox only)")
 
 	flag.Parse()
 
@@ -102,6 +103,9 @@ func main() {
 				OrderDescription: "Some useful tool",
 			},
 		}
+		if config.Server() == core.SandBoxBaseURL {
+			pa.Case = *pcase
+		}
 		fmt.Fprintf(os.Stderr, "Creating a %.2f payment ...\n", pa.PriceAmount)
 		pay, err := payments.New(pa)
 		if err != nil {
diff --git a/payments/payment.go b/payments/payment.go
index 6cdc940..908ec15 100644
--- a/payments/payment.go
+++ b/payments/payment.go
@@ -24,13 +24,27 @@ type PaymentAmount struct {
 type PaymentArgs struct {
 	PaymentAmount
 
-	FeePaidByUser  bool    `json:"is_fee_paid_by_user,omitempty"`
-	FixedRate      bool    `json:"fixed_rate,omitempty"`
-	PayoutAddress  string  `json:"payout_address,omitempty"`
-	PayAmount      float64 `json:"pay_amount,omitempty"`
-	PayoutCurrency string  `json:"payout_currency,omitempty"`
-	PayoutExtraID  string  `json:"payout_extra_id,omitempty"`
-	PurchaseID     string  `json:"purchase_id,omitempty"`
+	// FeePaidByUser is optional, required for fixed-rate exchanges with all fees paid by users.
+	FeePaidByUser bool `json:"is_fee_paid_by_user,omitempty"`
+	// FixedRate is optional, required for fixed-rate exchanges.
+	FixedRate bool `json:"fixed_rate,omitempty"`
+	// PayoutAddress is optional, usually the funds will go to the address you specify in
+	// your personal account. In case you want to receive funds on another address, you can specify
+	// it in this parameter.
+	PayoutAddress string `json:"payout_address,omitempty"`
+	// PayAmount is optional, the amount that users have to pay for the order stated in crypto.
+	// You can either specify it yourself, or we will automatically convert the amount indicated
+	// in price_amount.
+	PayAmount float64 `json:"pay_amount,omitempty"`
+	// PayoutCurrency for the cryptocurrency name.
+	PayoutCurrency string `json:"payout_currency,omitempty"`
+	// PayoutExtraID is optional, extra id or memo or tag for external payout_address.
+	PayoutExtraID string `json:"payout_extra_id,omitempty"`
+	// PurchaseID is optional, id of purchase for which you want to create another
+	// payment, only used for several payments for one order.
+	PurchaseID string `json:"purchase_id,omitempty"`
+	// optional, case which you want to test (sandbox only).
+	Case string `json:"case,omitempty"`
 }
 
 // Payment holds payment related information once we get a response