diff --git a/backend_api_python/app/services/factors/registry.py b/backend_api_python/app/services/factors/registry.py
index 4222d4709..fec8452a5 100644
--- a/backend_api_python/app/services/factors/registry.py
+++ b/backend_api_python/app/services/factors/registry.py
@@ -1077,8 +1077,21 @@ def _garman_klass_volatility(frame: pd.DataFrame, params: Mapping[str, Any]) ->
 
 def _amihud_illiquidity(frame: pd.DataFrame, params: Mapping[str, Any]) -> float:
     period = _period(params)
-    close = _require(frame["close"], period + 1)
-    volume = pd.to_numeric(frame["volume"], errors="coerce").iloc[-period:]
-    returns = close.pct_change().abs().iloc[-period:]
-    traded_value = (close.iloc[-period:] * volume).replace(0, np.nan)
-    return float((returns.to_numpy() / traded_value.to_numpy()).mean())
+    raw_close = pd.to_numeric(frame["close"], errors="coerce").replace([np.inf, -np.inf], np.nan)
+    raw_volume = pd.to_numeric(frame["volume"], errors="coerce").replace([np.inf, -np.inf], np.nan)
+    valid_close = raw_close.notna().to_numpy()
+    close_values = raw_close.to_numpy(dtype=float)[valid_close]
+    if len(close_values) < period + 1:
+        raise FactorError("factor.insufficientHistory")
+    tail_close = close_values[-(period + 1):]
+    prev_close = tail_close[:-1]
+    curr_close = tail_close[1:]
+    curr_volume = raw_volume.to_numpy(dtype=float)[valid_close][-period:]
+    with np.errstate(divide="ignore", invalid="ignore"):
+        abs_returns = np.abs(curr_close / prev_close - 1.0)
+        traded_value = curr_close * curr_volume
+        ratio = abs_returns / np.where(traded_value > 0.0, traded_value, np.nan)
+    finite = ratio[np.isfinite(ratio)]
+    if finite.size == 0:
+        return float("nan")
+    return float(finite.mean())
diff --git a/backend_api_python/tests/test_factor_registry.py b/backend_api_python/tests/test_factor_registry.py
index 6ca0c7833..3fc550f7a 100644
--- a/backend_api_python/tests/test_factor_registry.py
+++ b/backend_api_python/tests/test_factor_registry.py
@@ -138,3 +138,41 @@ def test_extended_factor_families_have_expected_invariants():
     assert compute_factor("parkinson_volatility", frame) > 0
     assert np.isfinite(compute_factor("skewness", frame))
     assert np.isfinite(compute_factor("kurtosis", frame))
+
+
+def test_amihud_illiquidity_aligns_close_and_volume_with_missing_or_zero_bars():
+    trailing_nan = pd.DataFrame({
+        "close": [100.0, 102.0, 101.0, 104.0, 103.0, 106.0, np.nan],
+        "volume": [1_000.0, 1_100.0, 1_200.0, 1_300.0, 1_400.0, 1_500.0, 1_600.0],
+    })
+    clean = trailing_nan.iloc[:-1]
+    assert compute_factor("amihud_illiquidity", trailing_nan, {"period": 5}) == pytest.approx(
+        compute_factor("amihud_illiquidity", clean, {"period": 5})
+    )
+
+    internal_nan_mismatch = pd.DataFrame({
+        "close": [100.0, 101.0, np.nan, 103.0, 104.0, np.nan, 106.0, 108.0],
+        "volume": [100.0, 200.0, 9_999.0, 300.0, 400.0, 9_999.0, 500.0, 600.0],
+    })
+    expected = compute_factor(
+        "amihud_illiquidity",
+        internal_nan_mismatch.dropna(subset=["close"]).reset_index(drop=True),
+        {"period": 4},
+    )
+    assert compute_factor("amihud_illiquidity", internal_nan_mismatch, {"period": 4}) == pytest.approx(
+        expected
+    )
+
+    zero_volume = pd.DataFrame({
+        "close": [100.0, 101.0, 102.0, 103.0, 104.0, 105.0],
+        "volume": [0.0, 0.0, 0.0, 0.0, 0.0, 0.0],
+    })
+    assert np.isnan(compute_factor("amihud_illiquidity", zero_volume, {"period": 5}))
+
+    short_close = pd.DataFrame({
+        "close": [100.0, np.nan, 102.0, 103.0],
+        "volume": [1_000.0, 1_000.0, 1_000.0, 1_000.0],
+    })
+    with pytest.raises(FactorError) as caught:
+        compute_factor("amihud_illiquidity", short_close, {"period": 5})
+    assert caught.value.code == "factor.insufficientHistory"
diff --git a/backend_api_python/tests/test_factor_research.py b/backend_api_python/tests/test_factor_research.py
index 8a1148351..7dc5c656f 100644
--- a/backend_api_python/tests/test_factor_research.py
+++ b/backend_api_python/tests/test_factor_research.py
@@ -459,3 +459,30 @@ def test_factor_research_warmup_bars_handles_shorthand_and_custom_multistage_fac
             [timestamp],
         )
         assert panel.loc[timestamp].notna().all(), factor_id
+
+
+def test_factor_research_correlation_survives_nan_close_in_amihud_illiquidity():
+    index = pd.date_range("2025-01-01", periods=60, freq="B")
+    frames = {}
+    for offset, symbol in enumerate(["A", "B", "C", "D", "E", "F"], start=1):
+        close = pd.Series([100.0 + day * (0.2 + offset * 0.05) for day in range(len(index))], index=index)
+        if symbol == "F":
+            close.iloc[40] = float("nan")
+        frames[symbol] = pd.DataFrame({
+            "open": close - 0.1,
+            "high": close + 1.0,
+            "low": close - 1.0,
+            "close": close,
+            "volume": [1_000.0 + day * 10.0 for day in range(len(index))],
+        }, index=index)
+
+    result = FactorResearchEngine().run(
+        frames=frames,
+        factor_id="momentum_20",
+        start_date=index[30],
+        end_date=index[-1],
+        groups=3,
+        holding_period=5,
+    )
+
+    assert "amihud_illiquidity" in result["factorCorrelation"]["factors"]