diff --git a/src/invoice.py b/src/invoice.py
index dbde63f..271c3d6 100755
--- a/src/invoice.py
+++ b/src/invoice.py
@@ -13,12 +13,23 @@
 import sys
 from datetime import datetime
 
-from reportlab.lib import colors
-from reportlab.lib.enums import TA_RIGHT
-from reportlab.lib.pagesizes import LETTER
-from reportlab.lib.styles import ParagraphStyle, getSampleStyleSheet
-from reportlab.platypus import (SimpleDocTemplate, Paragraph, Spacer, Table,
-                                TableStyle)
+# Reportlab is required for PDF generation. If it's missing, emit a clear
+# error message on stderr so callers can surface the failure to users.
+try:
+    from reportlab.lib import colors
+    from reportlab.lib.enums import TA_RIGHT
+    from reportlab.lib.pagesizes import LETTER
+    from reportlab.lib.styles import ParagraphStyle, getSampleStyleSheet
+    from reportlab.platypus import (
+        SimpleDocTemplate,
+        Paragraph,
+        Spacer,
+        Table,
+        TableStyle,
+    )
+except ModuleNotFoundError as exc:  # pragma: no cover - exercised via JS
+    print(str(exc), file=sys.stderr)
+    sys.exit(1)
 
 
 def _load_profile(base_dir):
@@ -174,8 +185,10 @@ def main():
 
     buffer = io.BytesIO()
     generate_invoice(buffer, invoice_data)
-    pdf_bytes = buffer.getvalue()
+    buffer.seek(0)
+    pdf_bytes = buffer.read()
     sys.stdout.write(base64.b64encode(pdf_bytes).decode("ascii"))
+    sys.stdout.flush()
 
 
 if __name__ == "__main__":
diff --git a/src/slurmcostmanager.js b/src/slurmcostmanager.js
index eef896a..b48035c 100644
--- a/src/slurmcostmanager.js
+++ b/src/slurmcostmanager.js
@@ -905,11 +905,26 @@ function Details({
     };
     try {
       setError(null);
+      if (!filteredDetails.length) {
+        setError('No usage data matches current filters');
+        return;
+      }
       const output = await window.cockpit.spawn(
         ['python3', `${PLUGIN_BASE}/invoice.py`],
         { input: JSON.stringify(invoiceData), err: 'out' }
       );
-      const byteChars = atob(output.trim());
+      const trimmed = output.trim();
+      if (!trimmed) {
+        setError('Invoice generation returned no data');
+        return;
+      }
+      let byteChars;
+      try {
+        byteChars = atob(trimmed);
+      } catch (decodeErr) {
+        setError(trimmed || decodeErr.message || String(decodeErr));
+        return;
+      }
       const byteNumbers = new Array(byteChars.length);
       for (let i = 0; i < byteChars.length; i++) {
         byteNumbers[i] = byteChars.charCodeAt(i);