diff --git a/docs/source/c_fx_smile.rst b/docs/source/c_fx_smile.rst
index af68ebc2..d01d19d1 100644
--- a/docs/source/c_fx_smile.rst
+++ b/docs/source/c_fx_smile.rst
@@ -404,8 +404,8 @@ this produces minor deviations from his calculated values.
    for op in ops:
        op.rate(fx=fxf)
 
-   strikes = [float(_._pricing["k"]) for _ in ops]
-   vols = [float(_._pricing["vol"]) for _ in ops]
+   strikes = [float(_._pricing.k) for _ in ops]
+   vols = [float(_._pricing.vol) for _ in ops]
    data2 = DataFrame(
        data=[strikes[0:3], vols[0:3], strikes[3:6], vols[3:6], strikes[6:9], vols[6:9]],
        index=[("1y", "k"), ("1y", "vol"), ("18m", "k"), ("18m", "vol"), ("2y", "k"), ("2y", "vol")],
diff --git a/docs/source/i_whatsnew.rst b/docs/source/i_whatsnew.rst
index 6099af8a..fc0a594f 100644
--- a/docs/source/i_whatsnew.rst
+++ b/docs/source/i_whatsnew.rst
@@ -101,6 +101,10 @@ email contact, see `rateslib <https://rateslib.com>`_.
        *FXRates* and *FXForwards* to allow auto-mutate detection of associated objects and ensure
        consistent method results.
        (`570 <https://github.com/attack68/rateslib/pull/570>`_)
+   * - Refactor
+     - The internal data objects for *FXOption* pricing are restructured to conform to more
+       strict data typing.
+       (`642 <https://github.com/attack68/rateslib/pull/642>`_)
 
 1.6.0 (30th November 2024)
 ****************************
diff --git a/python/rateslib/instruments/fx_volatility/strategies.py b/python/rateslib/instruments/fx_volatility/strategies.py
index 175da5bb..992a167f 100644
--- a/python/rateslib/instruments/fx_volatility/strategies.py
+++ b/python/rateslib/instruments/fx_volatility/strategies.py
@@ -40,7 +40,7 @@ class FXOptionStrat:
         The multiplier for the *'vol'* metric that sums the options to a final *rate*.
     """
 
-    _pricing: dict[str, Any]
+    _greeks: dict[str, Any] = {}
     _strat_elements: tuple[FXOption | FXOptionStrat, ...]
     periods: list[FXOption]
 
@@ -733,7 +733,7 @@ def d_wrt_sigma1(period_index, greeks, smile_greeks, vol, eta1):
             iters += 1
 
         if record_greeks:  # this needs to be explicitly called since it degrades performance
-            self._pricing["strangle_greeks"] = {
+            self._greeks["strangle"] = {
                 "single_vol": {
                     "FXPut": self.periods[0].analytic_greeks(curves, solver, fx, base, vol=tgt_vol),
                     "FXCall": self.periods[1].analytic_greeks(
@@ -900,16 +900,16 @@ def _maybe_set_vega_neutral_notional(self, curves, solver, fx, base, vol, metric
                 metric="single_vol",
                 record_greeks=True,
             )
-            self._pricing["straddle_greeks"] = self.periods[1].analytic_greeks(
+            self._greeks["straddle"] = self.periods[1].analytic_greeks(
                 curves,
                 solver,
                 fx,
                 base,
                 vol=vol[1],
             )
-            strangle_vega = self._pricing["strangle_greeks"]["market_vol"]["FXPut"]["vega"]
-            strangle_vega += self._pricing["strangle_greeks"]["market_vol"]["FXCall"]["vega"]
-            straddle_vega = self._pricing["straddle_greeks"]["vega"]
+            strangle_vega = self._greeks["strangle"]["market_vol"]["FXPut"]["vega"]
+            strangle_vega += self._greeks["strangle"]["market_vol"]["FXCall"]["vega"]
+            straddle_vega = self._greeks["straddle"]["vega"]
             scalar = strangle_vega / straddle_vega
             self.periods[1].kwargs["notional"] = float(
                 self.periods[0].periods[0].periods[0].notional * -scalar,
diff --git a/python/rateslib/instruments/fx_volatility/vanilla.py b/python/rateslib/instruments/fx_volatility/vanilla.py
index 91ae2f84..edcf4c9f 100644
--- a/python/rateslib/instruments/fx_volatility/vanilla.py
+++ b/python/rateslib/instruments/fx_volatility/vanilla.py
@@ -1,8 +1,9 @@
 from __future__ import annotations
 
 from abc import ABCMeta
+from dataclasses import dataclass
 from datetime import datetime
-from typing import TYPE_CHECKING, NamedTuple
+from typing import TYPE_CHECKING
 
 from pandas import DataFrame
 
@@ -10,7 +11,7 @@
 from rateslib.calendars import _get_fx_expiry_and_delivery, get_calendar
 from rateslib.curves import Curve
 from rateslib.curves._parsers import _validate_obj_not_no_input
-from rateslib.default import NoInput, _drb, plot
+from rateslib.default import NoInput, PlotOutput, _drb, plot
 from rateslib.dual.utils import _dual_float
 from rateslib.fx_volatility import FXVolObj
 from rateslib.instruments.sensitivities import Sensitivities
@@ -23,8 +24,11 @@
 from rateslib.periods import Cashflow, FXCallPeriod, FXPutPeriod
 
 if TYPE_CHECKING:
+    import numpy as np
+
     from rateslib.typing import (
         FX_,
+        NPV,
         Any,
         CalInput,
         Curves_,
@@ -32,19 +36,20 @@
         DualTypes,
         DualTypes_,
         FXVol_,
-        FXVolOption,
         FXVolOption_,
         Solver_,
         bool_,
         datetime_,
+        float_,
         int_,
         str_,
     )
 
 
-class PricingMetrics(NamedTuple):
-    vol: FXVolOption
-    k: DualTypes_
+@dataclass
+class _PricingMetrics:
+    vol: FXVolOption_
+    k: DualTypes
     delta_index: DualTypes | None
     spot: datetime
     t_e: DualTypes
@@ -141,7 +146,7 @@ class FXOption(Sensitivities, metaclass=ABCMeta):
 
     style: str = "european"
     _rate_scalar: float = 1.0
-    _pricing: dict[str, Any] = {}
+    _pricing: _PricingMetrics
 
     _option_periods: tuple[FXPutPeriod | FXCallPeriod]
     _cashflow_periods: tuple[Cashflow]
@@ -279,45 +284,47 @@ def _set_strike_and_vol(
         # and some of the pricing elements associated with this strike definition must
         # be captured for use in subsequent formulae.
         fx_ = _validate_fx_as_forwards(fx)
-        vol_: FXVolOption = _validate_obj_not_no_input(vol, "vol")  # type: ignore[assignment]
+        # vol_: FXVolOption = _validate_obj_not_no_input(vol, "vol")  # type: ignore[assignment]
+        vol_ = vol
         curves_3: Curve = _validate_obj_not_no_input(curves[3], "curves[3]")
         curves_1: Curve = _validate_obj_not_no_input(curves[1], "curves[1]")
 
-        self._pricing = {
-            "vol": vol_,
-            "k": self.kwargs["strike"],
-            "delta_index": None,
-            "spot": fx_.pairs_settlement[self.kwargs["pair"]],
-            "t_e": self._option_periods[0]._t_to_expiry(curves_3.node_dates[0]),
-            "f_d": fx_.rate(self.kwargs["pair"], self.kwargs["delivery"]),
-        }
+        self._pricing = _PricingMetrics(
+            vol=vol_,
+            k=self.kwargs["strike"],
+            delta_index=None,
+            spot=fx_.pairs_settlement[self.kwargs["pair"]],
+            t_e=self._option_periods[0]._t_to_expiry(curves_3.node_dates[0]),
+            f_d=fx_.rate(self.kwargs["pair"], self.kwargs["delivery"]),
+        )
+
         w_deli = curves_1[self.kwargs["delivery"]]
-        w_spot = curves_1[self._pricing["spot"]]
+        w_spot = curves_1[self._pricing.spot]
 
         if isinstance(self.kwargs["strike"], str):
             method = self.kwargs["strike"].lower()
 
             if method == "atm_forward":
-                self._pricing["k"] = fx_.rate(self.kwargs["pair"], self.kwargs["delivery"])
+                self._pricing.k = fx_.rate(self.kwargs["pair"], self.kwargs["delivery"])
 
             elif method == "atm_spot":
-                self._pricing["k"] = fx_.rate(self.kwargs["pair"], self._pricing["spot"])
+                self._pricing.k = fx_.rate(self.kwargs["pair"], self._pricing.spot)
 
             elif method == "atm_delta":
-                self._pricing["k"], self._pricing["delta_index"] = self._option_periods[
+                self._pricing.k, self._pricing.delta_index = self._option_periods[
                     0
                 ]._strike_and_index_from_atm(
                     delta_type=self._option_periods[0].delta_type,
-                    vol=vol_,
+                    vol=_validate_obj_not_no_input(vol_, "vol"),  # type: ignore[arg-type]
                     w_deli=w_deli,
                     w_spot=w_spot,
-                    f=self._pricing["f_d"],
-                    t_e=self._pricing["t_e"],
+                    f=self._pricing.f_d,
+                    t_e=self._pricing.t_e,
                 )
 
             elif method[-1] == "d":  # representing delta
                 # then strike is commanded by delta
-                self._pricing["k"], self._pricing["delta_index"] = self._option_periods[
+                self._pricing.k, self._pricing.delta_index = self._option_periods[
                     0
                 ]._strike_and_index_from_delta(
                     delta=float(self.kwargs["strike"][:-1]) / 100.0,
@@ -325,8 +332,8 @@ def _set_strike_and_vol(
                     vol=vol_,
                     w_deli=w_deli,
                     w_spot=w_spot,
-                    f=self._pricing["f_d"],
-                    t_e=self._pricing["t_e"],
+                    f=self._pricing.f_d,
+                    t_e=self._pricing.t_e,
                 )
 
             # TODO: this may affect solvers dependent upon sensitivity to vol for changing strikes.
@@ -335,20 +342,20 @@ def _set_strike_and_vol(
             # IRS for mid-market.
 
             # self.periods[0].strike = self._pricing["k"]
-            self._option_periods[0].strike = _dual_float(self._pricing["k"])
+            self._option_periods[0].strike = _dual_float(self._pricing.k)
 
         if isinstance(vol_, FXVolObj):
-            if self._pricing["delta_index"] is None:
-                self._pricing["delta_index"], self._pricing["vol"], _ = vol_.get_from_strike(
-                    k=self._pricing["k"],
-                    f=self._pricing["f_d"],
+            if self._pricing.delta_index is None:
+                self._pricing.delta_index, self._pricing.vol, _ = vol_.get_from_strike(
+                    k=self._pricing.k,
+                    f=self._pricing.f_d,
                     w_deli=w_deli,
                     w_spot=w_spot,
                     expiry=self.kwargs["expiry"],
                 )
             else:
-                self._pricing["vol"] = vol_._get_index(
-                    self._pricing["delta_index"],
+                self._pricing.vol = vol_._get_index(
+                    self._pricing.delta_index,
                     self.kwargs["expiry"],
                 )
 
@@ -361,7 +368,7 @@ def _set_premium(self, curves: Curves_DiscTuple, fx: FX_ = NoInput(0)) -> None:
                     _validate_obj_not_no_input(curves[1], "curves[1]"),
                     curves_3,
                     fx,
-                    vol=self._pricing["vol"],
+                    vol=self._pricing.vol,
                     local=False,
                 )
             except AttributeError:
@@ -451,10 +458,15 @@ def rate(
 
         metric = _drb(self.kwargs["metric"], metric)
         if metric in ["vol", "single_vol"]:
-            return self._pricing["vol"]
-
-        _: DualTypes = self.periods[0].rate(
-            curves_[1], curves_[3], fx_, NoInput(0), False, self._pricing["vol"]
+            return _validate_obj_not_no_input(self._pricing.vol, "vol")  # type: ignore[return-value]
+
+        _: DualTypes = self._option_periods[0].rate(
+            disc_curve=_validate_obj_not_no_input(curves_[1], "curve"),
+            disc_curve_ccy2=_validate_obj_not_no_input(curves_[3], "curve"),
+            fx=fx_,
+            base=NoInput(0),
+            local=False,
+            vol=self._pricing.vol,
         )
         if metric == "premium":
             if self.periods[0].metric == "pips":
@@ -470,8 +482,8 @@ def npv(
         fx: FX_ = NoInput(0),
         base: str_ = NoInput(0),
         local: bool = False,
-        vol: float = NoInput(0),
-    ):
+        vol: FXVol_ = NoInput(0),
+    ) -> NPV:
         """
         Return the NPV of the *Option*.
 
@@ -510,16 +522,23 @@ def npv(
         self._set_strike_and_vol(curves_, fx_, vol_)
         self._set_premium(curves_, fx_)
 
-        opt_npv = self._option_periods[0].npv(curves_[1], curves_[3], fx_, base_, local, vol_)
+        opt_npv = self._option_periods[0].npv(
+            disc_curve=_validate_obj_not_no_input(curves_[1], "curve_[1]"),
+            disc_curve_ccy2=_validate_obj_not_no_input(curves_[3], "curve_[3]"),
+            fx=fx_,
+            base=base_,
+            local=local,
+            vol=vol_,
+        )
         if self.kwargs["premium_ccy"] == self.kwargs["pair"][:3]:
             disc_curve = curves_[1]
         else:
             disc_curve = curves_[3]
         prem_npv = self._cashflow_periods[0].npv(NoInput(0), disc_curve, fx, base, local)
         if local:
-            return {k: opt_npv.get(k, 0) + prem_npv.get(k, 0) for k in set(opt_npv) | set(prem_npv)}
+            return {k: opt_npv.get(k, 0) + prem_npv.get(k, 0) for k in set(opt_npv) | set(prem_npv)}  # type:ignore[union-attr, arg-type]
         else:
-            return opt_npv + prem_npv
+            return opt_npv + prem_npv  # type: ignore[operator]
 
     def cashflows(
         self,
@@ -527,8 +546,8 @@ def cashflows(
         solver: Solver_ = NoInput(0),
         fx: FX_ = NoInput(0),
         base: str_ = NoInput(0),
-        vol: float = NoInput(0),
-    ):
+        vol: FXVol_ = NoInput(0),
+    ) -> DataFrame:
         """
         Return the properties of all periods used in calculating cashflows.
 
@@ -567,8 +586,14 @@ def cashflows(
         self._set_premium(curves_, fx_)
 
         seq = [
-            self.periods[0].cashflows(curves_[1], curves_[3], fx_, base_, vol=vol_),
-            self.periods[1].cashflows(curves_[1], curves_[3], fx_, base_),
+            self._option_periods[0].cashflows(
+                disc_curve=_validate_obj_not_no_input(curves_[1], "curves_[1]"),
+                disc_curve_ccy2=_validate_obj_not_no_input(curves_[3], "curves_[3]"),
+                fx=fx_,
+                base=base_,
+                vol=vol_,
+            ),
+            self._cashflow_periods[0].cashflows(curves_[1], curves_[3], fx_, base_),
         ]
         return DataFrame.from_records(seq)
 
@@ -579,8 +604,8 @@ def analytic_greeks(
         fx: FX_ = NoInput(0),
         base: str_ = NoInput(0),
         local: bool = False,
-        vol: float = NoInput(0),
-    ):
+        vol: FXVol_ = NoInput(0),
+    ) -> dict[str, Any]:
         """
         Return various pricing metrics of the *FX Option*.
 
@@ -620,12 +645,12 @@ def analytic_greeks(
         # self._set_premium(curves, fx)
 
         return self._option_periods[0].analytic_greeks(
-            curves_[1],
-            curves_[3],
-            fx_,
-            base_,
-            local,
-            vol_,
+            disc_curve=_validate_obj_not_no_input(curves_[1], "curves_[1]"),
+            disc_curve_ccy2=_validate_obj_not_no_input(curves_[3], "curves_[3]"),
+            fx=_validate_fx_as_forwards(fx_),
+            base=base_,
+            local=local,
+            vol=vol_,
             premium=NoInput(0),
         )
 
@@ -637,8 +662,10 @@ def _plot_payoff(
         fx: FX_ = NoInput(0),
         base: str_ = NoInput(0),
         local: bool = False,
-        vol: float = NoInput(0),
-    ):
+        vol: FXVol_ = NoInput(0),
+    ) -> tuple[
+        np.ndarray[tuple[int], np.dtype[np.float64]], np.ndarray[tuple[int], np.dtype[np.float64]]
+    ]:
         """
         Mechanics to determine (x,y) coordinates for payoff at expiry plot.
         """
@@ -666,10 +693,10 @@ def plot_payoff(
         fx: FX_ = NoInput(0),
         base: str_ = NoInput(0),
         local: bool = False,
-        vol: float = NoInput(0),
-    ):
+        vol: float_ = NoInput(0),
+    ) -> PlotOutput:
         x, y = self._plot_payoff(range, curves, solver, fx, base, local, vol)
-        return plot(x, [y])
+        return plot(x, [y])  # type: ignore
 
 
 class FXCall(FXOption):
@@ -679,7 +706,7 @@ class FXCall(FXOption):
     For parameters see :class:`~rateslib.instruments.FXOption`.
     """
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
         super().__init__(*args, **kwargs)
         self._option_periods = (
             FXCallPeriod(
@@ -705,7 +732,7 @@ class FXPut(FXOption):
     For parameters see :class:`~rateslib.instruments.FXOption`.
     """
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
         super().__init__(*args, **kwargs)
         self._option_periods = (
             FXPutPeriod(
diff --git a/python/rateslib/periods.py b/python/rateslib/periods.py
index 051d75aa..bc5b6c46 100644
--- a/python/rateslib/periods.py
+++ b/python/rateslib/periods.py
@@ -74,6 +74,7 @@
         Curve_,
         CurveOption_,
         DualTypes,
+        DualTypes_,
         FXVolOption,
         FXVolOption_,
         Number,
@@ -3334,10 +3335,10 @@ def cashflows(
         self,
         disc_curve: Curve,
         disc_curve_ccy2: Curve,
-        fx: float | FXRates | FXForwards | NoInput = NoInput(0),
-        base: str | NoInput = NoInput(0),
+        fx: FX_ = NoInput(0),
+        base: str_ = NoInput(0),
         local: bool = False,
-        vol: DualTypes | FXVols | NoInput = NoInput(0),
+        vol: FXVolOption_ = NoInput(0),
     ) -> dict[str, Any]:
         """
         Return the properties of the period used in calculating cashflows.
@@ -3473,11 +3474,11 @@ def rate(
         self,
         disc_curve: Curve,
         disc_curve_ccy2: Curve,
-        fx: float | FXRates | FXForwards | NoInput = NoInput(0),
-        base: str | NoInput = NoInput(0),
+        fx: FX_ = NoInput(0),
+        base: str_ = NoInput(0),
         local: bool = False,
-        vol: DualTypes | FXVols | NoInput = NoInput(0),
-        metric: str | NoInput = NoInput(0),
+        vol: FXVolOption_ = NoInput(0),
+        metric: str_ = NoInput(0),
     ) -> DualTypes:
         """
         Return the pricing metric of the *FXOption*.
@@ -3597,10 +3598,10 @@ def analytic_greeks(
         disc_curve: Curve,
         disc_curve_ccy2: Curve,
         fx: FXForwards,
-        base: str | NoInput = NoInput(0),
+        base: str_ = NoInput(0),
         local: bool = False,
-        vol: DualTypes | FXVols | NoInput = NoInput(0),
-        premium: DualTypes | NoInput = NoInput(0),  # expressed in the payment currency
+        vol: FXVolOption_ = NoInput(0),
+        premium: DualTypes_ = NoInput(0),  # expressed in the payment currency
     ) -> dict[str, Any]:
         r"""
         Return the different greeks for the *FX Option*.
@@ -3890,7 +3891,7 @@ def _strike_and_index_from_atm(
         w_deli: DualTypes,
         w_spot: DualTypes,
         f: DualTypes,
-        t_e: float,
+        t_e: DualTypes,
     ) -> tuple[DualTypes, DualTypes | None]:
         # TODO this method branches depending upon eta0 and eta1, but depending upon the
         # type of vol these maybe automatcially set equal to each other. Refactorin this would
@@ -3951,7 +3952,7 @@ def _strike_and_index_from_delta(
         w_deli: DualTypes,
         w_spot: DualTypes,
         f: DualTypes,
-        t_e: float,
+        t_e: DualTypes,
     ) -> tuple[DualTypes, DualTypes | None]:
         vol_delta_type = _get_vol_delta_type(vol, delta_type)
 
@@ -3993,7 +3994,7 @@ def _strike_and_index_from_delta(
         _2: DualTypes | None = delta_idx
         return _1, _2
 
-    def _moneyness_from_atm_delta_closed_form(self, vol: DualTypes, t_e: float) -> DualTypes:
+    def _moneyness_from_atm_delta_closed_form(self, vol: DualTypes, t_e: DualTypes) -> DualTypes:
         """
         Return `u` given premium unadjusted `delta`, of either 'spot' or 'forward' type.
 
@@ -4291,7 +4292,7 @@ def _moneyness_from_atm_delta_two_dimensional(
         self,
         delta_type: str,
         vol: FXDeltaVolSmile,
-        t_e: float,
+        t_e: DualTypes,
         z_w: DualTypes,
     ) -> tuple[DualTypes, DualTypes]:
         def root2d(
@@ -4454,7 +4455,7 @@ def root3d(
 
     def _get_vol_maybe_from_obj(
         self,
-        vol: FXVols | DualTypes | NoInput,
+        vol: FXVolOption_,
         fx: FXForwards,
         disc_curve: Curve,
     ) -> DualTypes:
diff --git a/python/rateslib/typing.py b/python/rateslib/typing.py
index c3075a70..dec53fc1 100644
--- a/python/rateslib/typing.py
+++ b/python/rateslib/typing.py
@@ -98,6 +98,7 @@
 bool_: TypeAlias = "bool | NoInput"
 int_: TypeAlias = "int | NoInput"
 datetime_: TypeAlias = "datetime | NoInput"
+float_: TypeAlias = "float | NoInput"
 
 from rateslib.curves import Curve as Curve  # noqa: E402
 
diff --git a/python/tests/test_instruments.py b/python/tests/test_instruments.py
index 583210d8..e4d79083 100644
--- a/python/tests/test_instruments.py
+++ b/python/tests/test_instruments.py
@@ -4785,6 +4785,21 @@ def test_expiry_delivery_tenor_eom(self, evald, eom, expected) -> None:
         )
         assert fxo.kwargs["expiry"] == expected
 
+    def test_single_vol_not_no_input(self, fxfo):
+        fxo = FXCall(
+            pair="eurusd",
+            expiry=dt(2023, 6, 16),
+            delivery_lag=dt(2023, 6, 20),
+            payment_lag=dt(2023, 6, 20),
+            curves=[None, fxfo.curve("eur", "eur"), None, fxfo.curve("usd", "eur")],
+            delta_type="forward",
+            premium_ccy="usd",
+            strike=1.1,
+            notional=1e6,
+        )
+        with pytest.raises(ValueError, match="`vol` must be supplied. Got"):
+            fxo.rate(metric="vol", fx=fxfo)
+
 
 class TestRiskReversal:
     @pytest.mark.parametrize(