diff --git a/README.md b/README.md
index 73aa38ea9..8dcc80d60 100644
--- a/README.md
+++ b/README.md
@@ -82,9 +82,12 @@ Run `python core.py validate --help` to see the list of validation options.
   -o, --output TEXT               Report output file destination and name. Path will be
                                   relative to the validation execution directory
                                   and should end in the desired output filename
-                                  without file extension
-                                  '/user/reports/result' will be 'user/report' directory
-                                  with the filename as 'result'
+                                  without file extension. The file extension will be
+                                  automatically added based on the output format.
+                                  Example: 'reports/result' will create 'reports' directory
+                                  with the filename 'result.json' (or 'result.xlsx' for Excel).
+                                  Note: Provide a valid, writable path. Absolute paths must
+                                  be valid for your operating system.
   -of, --output-format [JSON|XLSX]
                                   Output file format
   -rr, --raw-report               Report in a raw format as it is generated by
diff --git a/cdisc_rules_engine/constants/__init__.py b/cdisc_rules_engine/constants/__init__.py
index 0453d6f1f..e61d21310 100644
--- a/cdisc_rules_engine/constants/__init__.py
+++ b/cdisc_rules_engine/constants/__init__.py
@@ -15,3 +15,5 @@
 )
 
 NULL_FLAVORS = ["", None, {None}, [], {}, np.nan]
+
+KNOWN_REPORT_EXTENSIONS = [".json", ".xlsx", ".xls"]
diff --git a/cdisc_rules_engine/services/reporting/base_report.py b/cdisc_rules_engine/services/reporting/base_report.py
index 3fc37311a..16b5180eb 100644
--- a/cdisc_rules_engine/services/reporting/base_report.py
+++ b/cdisc_rules_engine/services/reporting/base_report.py
@@ -1,6 +1,7 @@
 from abc import ABC, abstractmethod
 from io import IOBase
 
+from cdisc_rules_engine.constants import KNOWN_REPORT_EXTENSIONS
 from cdisc_rules_engine.models.validation_args import Validation_args
 from cdisc_rules_engine.services.reporting.base_report_data import (
     BaseReportData,
@@ -21,7 +22,23 @@ def __init__(
         self._report_standard = report_standard
         self._args = args
         self._template = template
-        self._output_name: str = f"{self._args.output}.{self._file_ext}"
+        self._output_name: str = self._get_output_filename()
+
+    def _get_output_filename(self) -> str:
+        expected_ext = f".{self._file_ext}"
+        output_path = self._args.output
+
+        if output_path.lower().endswith(expected_ext.lower()):
+            base_path = output_path[: -len(expected_ext)]
+            return f"{base_path}{expected_ext}"
+
+        path_lower = output_path.lower()
+        for ext in KNOWN_REPORT_EXTENSIONS:
+            if path_lower.endswith(ext):
+                base_path = output_path[: -len(ext)]
+                return f"{base_path}{expected_ext}"
+
+        return f"{output_path}{expected_ext}"
 
     @property
     @abstractmethod
diff --git a/cdisc_rules_engine/services/reporting/excel_report.py b/cdisc_rules_engine/services/reporting/excel_report.py
index 6011c58fb..a40d27a4a 100644
--- a/cdisc_rules_engine/services/reporting/excel_report.py
+++ b/cdisc_rules_engine/services/reporting/excel_report.py
@@ -85,9 +85,22 @@ def write_report(self):
         logger = logging.getLogger("validator")
         try:
             report_data = self.get_export()
+            output_dir = os.path.dirname(self._output_name)
+            if output_dir:
+                try:
+                    os.makedirs(output_dir, exist_ok=True)
+                except OSError as e:
+                    error_msg = (
+                        f"Cannot create output directory '{output_dir}': {e.strerror}. "
+                        f"Please provide a valid, writable path for the output file."
+                    )
+                    logger.error(error_msg)
+                    raise OSError(error_msg) from e
             with open(self._output_name, "wb") as f:
                 f.write(excel_workbook_to_stream(report_data))
             logger.debug(f"Report written to: {self._output_name}")
+        except OSError:
+            raise
         except Exception as e:
             logger.error(f"Error writing report: {e}")
             raise e
diff --git a/cdisc_rules_engine/services/reporting/json_report.py b/cdisc_rules_engine/services/reporting/json_report.py
index 4aadf7a56..3c1a32b2b 100644
--- a/cdisc_rules_engine/services/reporting/json_report.py
+++ b/cdisc_rules_engine/services/reporting/json_report.py
@@ -1,4 +1,5 @@
 import json
+import os
 from typing import BinaryIO, override
 
 from cdisc_rules_engine.enums.report_types import ReportTypes
@@ -66,5 +67,14 @@ def write_report(self):
         report_data = self.get_export(
             raw_report=self._args.raw_report,
         )
+        output_dir = os.path.dirname(self._output_name)
+        if output_dir:
+            try:
+                os.makedirs(output_dir, exist_ok=True)
+            except OSError as e:
+                raise OSError(
+                    f"Cannot create output directory '{output_dir}': {e.strerror}. "
+                    f"Please provide a valid, writable path for the output file."
+                ) from e
         with open(self._output_name, "w") as f:
             json.dump(report_data, f)
diff --git a/scripts/run_validation.py b/scripts/run_validation.py
index 3e08fddfc..5b6e427d6 100644
--- a/scripts/run_validation.py
+++ b/scripts/run_validation.py
@@ -199,9 +199,14 @@ def run_validation(args: Validation_args):
             datasets, results, elapsed_time, args, data_service, dictionary_versions
         )
         reporting_services: List[BaseReport] = reporting_factory.get_report_services()
+        output_files = []
         for reporting_service in reporting_services:
             reporting_service.write_report()
-        print(f"Output: {args.output}")
+            output_files.append(reporting_service._output_name)
+        if len(output_files) == 1:
+            print(f"Output: {output_files[0]}")
+        else:
+            print(f"Output: {', '.join(output_files)}")
     finally:
         if created_files:
             engine_logger.info(" Report generated, Cleaning up intermediate files")