diff --git a/riskqueue/data/validation.py b/riskqueue/data/validation.py
index 5c26649..6ab047f 100644
--- a/riskqueue/data/validation.py
+++ b/riskqueue/data/validation.py
@@ -19,6 +19,21 @@ class DataValidationError(ValueError):
     """Raised when transaction data cannot be used safely."""
 
 
+def _numeric_column(data: pd.DataFrame, column: str) -> pd.Series:
+    """Return a finite numeric column or raise the public validation error."""
+    try:
+        values = pd.to_numeric(data[column], errors="raise")
+        raw_values = values.to_numpy()
+        if np.iscomplexobj(raw_values):
+            raise ValueError
+        numeric_values = raw_values.astype(float)
+    except (TypeError, ValueError, OverflowError):
+        raise DataValidationError(f"{column} must contain numeric values") from None
+    if not np.isfinite(numeric_values).all():
+        raise DataValidationError(f"{column} must contain finite numeric values")
+    return values
+
+
 def validate_transactions(frame: pd.DataFrame) -> pd.DataFrame:
     """Validate the minimum PaySim-compatible contract and return a copy."""
     missing = REQUIRED_COLUMNS.difference(frame.columns)
@@ -29,13 +44,25 @@ def validate_transactions(frame: pd.DataFrame) -> pd.DataFrame:
         raise DataValidationError("Dataset is empty")
     if data[list(REQUIRED_COLUMNS)].isnull().any().any():
         raise DataValidationError("Required columns contain null values")
-    if not np.isfinite(data["amount"].astype(float)).all() or (data["amount"] < 0).any():
+
+    amount = _numeric_column(data, "amount")
+    if (amount < 0).any():
         raise DataValidationError("amount must contain finite non-negative values")
+    data["amount"] = amount.astype(float)
+
+    step = _numeric_column(data, "step")
+    if (step < 0).any() or (step % 1 != 0).any():
+        raise DataValidationError("step must contain finite non-negative integers")
+    if (step > np.iinfo(np.int64).max).any():
+        raise DataValidationError("step exceeds the supported integer range")
+    data["step"] = step.astype(np.int64)
+
+    labels = _numeric_column(data, "isFraud")
+    if not labels.isin([0, 1]).all():
+        raise DataValidationError("isFraud must be binary")
+    data["isFraud"] = labels.astype(np.int64)
+
     invalid_types = set(data["type"]).difference(TRANSACTION_TYPES)
     if invalid_types:
         raise DataValidationError(f"Invalid transaction types: {sorted(invalid_types)}")
-    if not set(data["isFraud"].unique()).issubset({0, 1}):
-        raise DataValidationError("isFraud must be binary")
-    if (data["step"] < 0).any():
-        raise DataValidationError("step must be non-negative")
     return data.sort_values(["step"], kind="stable").reset_index(drop=True)
diff --git a/tests/test_validation.py b/tests/test_validation.py
index d79e2ee..56f762e 100644
--- a/tests/test_validation.py
+++ b/tests/test_validation.py
@@ -22,6 +22,36 @@ def test_invalid_amounts(transactions, amount):
         validate_transactions(transactions)
 
 
+@pytest.mark.parametrize(
+    ("column", "value"),
+    [
+        ("amount", "not-a-number"),
+        ("step", "not-a-step"),
+        ("step", 1.5),
+        ("step", np.iinfo(np.int64).max + 1),
+        ("isFraud", "yes"),
+        ("isFraud", 2),
+    ],
+)
+def test_malformed_numeric_values_raise_validation_error(transactions, column, value):
+    transactions[column] = transactions[column].astype(object)
+    transactions.loc[0, column] = value
+    with pytest.raises(DataValidationError, match=column):
+        validate_transactions(transactions)
+
+
+def test_numeric_strings_are_normalized(transactions):
+    transactions["amount"] = transactions.amount.astype(str)
+    transactions["step"] = transactions.step.astype(str)
+    transactions["isFraud"] = transactions.isFraud.astype(str)
+
+    result = validate_transactions(transactions)
+
+    assert result.amount.dtype.kind == "f"
+    assert result.step.dtype == np.dtype("int64")
+    assert result.isFraud.dtype == np.dtype("int64")
+
+
 def test_unknown_type(transactions):
     transactions.loc[0, "type"] = "WIRE"
     with pytest.raises(DataValidationError, match="Invalid transaction"):