diff --git a/ns_app/api/payments.py b/ns_app/api/payments.py
new file mode 100644
index 0000000..a8d5740
--- /dev/null
+++ b/ns_app/api/payments.py
@@ -0,0 +1,119 @@
+import requests
+import frappe
+
+
+# Checks to see if customer has Autopay on
+@frappe.whitelist()
+def check_autopay(customer):
+    cust = frappe.get_doc("Customer", customer)
+
+    return {
+        "autopay_enabled": bool(cust.auto_pay),
+        "autopay_id": cust.auto_pay_id if cust.auto_pay else None
+    }
+
+
+
+# Creates payload to send through API, checks for success, then makes a call to create a payment entry.
+@frappe.whitelist()
+def run_autopay_payment(invoice, autopay_id, amount):
+
+    payload = {
+        "autopay_id": autopay_id,
+        "amount": amount,
+        "invoice": invoice
+    }
+
+    response = call_payment_api(payload)
+
+    # Handle gateway failure clearly
+    if not response.get("success"):
+        frappe.throw(response.get("error", "Payment failed"))
+
+    # Create ERPNext payment record
+    payment_entry = create_payment_entry(
+        invoice=invoice,
+        amount=amount,
+        transaction_id=response.get("transaction_id")
+    )
+
+    return {
+        "message": "AutoPay payment successful",
+        "payment_entry": payment_entry
+    }
+
+
+
+# Call's Crystal CLear's API and Runs an AutoPay transaction using NMI / Crystal Clear using customer_vault_id (autopay_id)
+    
+def call_payment_api(payload):
+
+    url = "https://crystalclear.transactiongateway.com/api/transact.php"
+
+    # Store these in site_config.json or environment variables
+    api_username = frappe.conf.get("nmi_username")
+    api_password = frappe.conf.get("nmi_password")
+
+    if not api_username or not api_password:
+        frappe.throw("Payment gateway credentials not configured")
+
+    data = {
+        "username": api_username,
+        "password": api_password,
+        "type": "sale",
+        "customer_vault_id": payload["autopay_id"],
+        "amount": payload["amount"],
+        "orderid": payload["invoice"],
+        "response": "json"
+    }
+
+    try:
+        response = requests.post(url, data=data, timeout=30)
+        response.raise_for_status()
+        result = response.json()
+
+    except Exception as e:
+        frappe.log_error(frappe.get_traceback(), "NMI Payment API Error")
+        frappe.throw("Payment processor unreachable")
+
+    # NMI success condition
+    if result.get("response") == "1":
+        return {
+            "success": True,
+            "transaction_id": result.get("transactionid")
+        }
+
+    # Failure case
+    return {
+        "success": False,
+        "error": result.get("responsetext", "Payment failed")
+    }
+
+
+
+# Auto creates payment entry in ERP Next
+def create_payment_entry(invoice, amount, transaction_id=None):
+    inv = frappe.get_doc("Sales Invoice", invoice)
+
+    pe = frappe.new_doc("Payment Entry")
+    pe.payment_type = "Receive"
+    pe.party_type = "Customer"
+    pe.party = inv.customer
+    pe.paid_amount = amount
+    pe.received_amount = amount
+    pe.reference_no = transaction_id
+    pe.reference_date = frappe.utils.nowdate()
+
+    pe.append("references", {
+        "reference_doctype": "Sales Invoice",
+        "reference_name": invoice,
+        "allocated_amount": amount
+    })
+
+    pe.insert()
+    pe.submit()
+
+    return pe.name
+
+
+
diff --git a/ns_app/hooks.py b/ns_app/hooks.py
index 3cfa4f4..d713671 100644
--- a/ns_app/hooks.py
+++ b/ns_app/hooks.py
@@ -7,4 +7,5 @@ app_license = "MIT"
 
 app_include_js = [
     "/assets/ns_app/js/custom.js"
+     "/assets/ns_app/js/sales_invoice.js"
 ]
diff --git a/ns_app/public/js/sales_invoice.js b/ns_app/public/js/sales_invoice.js
new file mode 100644
index 0000000..29c7749
--- /dev/null
+++ b/ns_app/public/js/sales_invoice.js
@@ -0,0 +1,68 @@
+frappe.ui.form.on("Sales Invoice", {
+    refresh(frm) {
+        if (frm.doc.docstatus !== 1) return; // submitted only
+
+        frm.add_custom_button("Run Payment", () => {
+            run_payment_flow(frm);
+        });
+    }
+});
+
+function run_payment_flow(frm) {
+    frappe.call({
+        method: "ns_app.api.payments.check_autopay",
+        args: {
+            customer: frm.doc.customer
+        },
+        callback(r) {
+            if (!r.message) return;
+
+            if (r.message.autopay_enabled) {
+                run_autopay(frm, r.message.autopay_id);
+            } else {
+                open_manual_payment_form(frm);
+            }
+        }
+    });
+
+
+function run_autopay(frm, autopay_id) {
+    frappe.confirm(
+        `Run AutoPay for $${frm.doc.grand_total}?`,
+        () => {
+            frappe.call({
+                method: "ns_app.api.payments.run_autopay_payment",
+                args: {
+                    invoice: frm.doc.name,
+                    autopay_id: autopay_id,
+                    amount: frm.doc.grand_total
+                },
+                callback(r) {
+                    frappe.msgprint(r.message || "Payment processed");
+                    frm.reload_doc();
+                }
+            });
+        }
+    );
+}
+
+
+function open_manual_payment_form(frm) {
+    const dialog = new frappe.ui.Dialog({
+        title: "Enter Payment",
+        fields: [
+            {
+                fieldtype: "HTML",
+                fieldname: "payment_form",
+                options: `<iframe
+                    src="https://payments.yourprovider.com/pay?invoice=${frm.doc.name}&amount=${frm.doc.grand_total}"
+                    style="width:100%;height:500px;border:none;"
+                ></iframe>`
+            }    
+        ]
+    });
+
+    dialog.show();
+}
+
+}