diff --git a/openfisca_core/periods/period_.py b/openfisca_core/periods/period_.py
index f7b901c58..11a7b671b 100644
--- a/openfisca_core/periods/period_.py
+++ b/openfisca_core/periods/period_.py
@@ -1,10 +1,10 @@
 from __future__ import annotations
 
 import typing
+from collections.abc import Sequence
 
 import calendar
 import datetime
-from collections.abc import Sequence
 
 import pendulum
 
diff --git a/openfisca_core/simulations/__init__.py b/openfisca_core/simulations/__init__.py
index 913e90d1e..c5db39e11 100644
--- a/openfisca_core/simulations/__init__.py
+++ b/openfisca_core/simulations/__init__.py
@@ -27,11 +27,14 @@
     SpiralError,
 )
 
+from .actions import RunFormula
 from .helpers import (  # noqa: F401
     calculate_output_add,
     calculate_output_divide,
     check_type,
     transform_to_strict_syntax,
 )
-from .simulation import Simulation  # noqa: F401
-from .simulation_builder import SimulationBuilder  # noqa: F401
+from .simulation import Simulation
+from .simulation_builder import SimulationBuilder
+
+__all__ = ["RunFormula", "Simulation", "SimulationBuilder"]
diff --git a/openfisca_core/simulations/actions/__init__.py b/openfisca_core/simulations/actions/__init__.py
new file mode 100644
index 000000000..df278c8cd
--- /dev/null
+++ b/openfisca_core/simulations/actions/__init__.py
@@ -0,0 +1,3 @@
+from ._run_formula import RunFormula
+
+__all__ = ["RunFormula"]
diff --git a/openfisca_core/simulations/actions/_run_formula.py b/openfisca_core/simulations/actions/_run_formula.py
new file mode 100644
index 000000000..eab3c1a26
--- /dev/null
+++ b/openfisca_core/simulations/actions/_run_formula.py
@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+from numpy.typing import NDArray
+from typing import Any, cast
+
+import dataclasses
+import inspect
+
+from ..typing import Formula2, Formula3, Instant, Params, Population
+
+
+@dataclasses.dataclass(frozen=True)
+class RunFormula:
+    """Run a Variable's given Formula."""
+
+    #: The formula we want to run.
+    formula: Formula3 | Formula2 | None = None
+
+    def __call__(
+        self, population: Population, instant: Instant, params: Params
+    ) -> NDArray[Any] | None:
+        if self.formula is None:
+            return None
+
+        if self.__arity() == 3:
+            return cast(Formula3, self.formula)(population, instant, params)
+
+        else:
+            return cast(Formula2, self.formula)(population, instant)
+
+    def __arity(self) -> int:
+        return len(inspect.getfullargspec(self.formula).args)
diff --git a/openfisca_core/simulations/simulation.py b/openfisca_core/simulations/simulation.py
index 95c90a9ee..2bd4e6fb7 100644
--- a/openfisca_core/simulations/simulation.py
+++ b/openfisca_core/simulations/simulation.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from openfisca_core.types import Population, TaxBenefitSystem, Variable
 from typing import Dict, NamedTuple, Optional, Set
 
 import tempfile
@@ -16,9 +17,11 @@
     SimpleTracer,
     TracingParameterNodeAtInstant,
 )
-from openfisca_core.types import Population, TaxBenefitSystem, Variable
 from openfisca_core.warnings import TempfileWarning
 
+from .actions import RunFormula
+from .typing import Params
+
 
 class Simulation:
     """
@@ -29,6 +32,13 @@ class Simulation:
     populations: Dict[str, Population]
     invalidated_caches: Set[Cache]
 
+    @property
+    def params(self) -> Params:
+        if self.trace:
+            return self.trace_parameters_at_instant
+
+        return self.tax_benefit_system.get_parameters_at_instant
+
     def __init__(
         self,
         tax_benefit_system: TaxBenefitSystem,
@@ -144,7 +154,8 @@ def _calculate(self, variable_name: str, period: Period):
         # First, try to run a formula
         try:
             self._check_for_cycle(variable.name, period)
-            array = self._run_formula(variable, population, period)
+            run_formula = RunFormula(variable.get_formula(period))
+            array = run_formula(population, period, self.params)
 
             # If no result, use the default value and cache it
             if array is None:
@@ -306,27 +317,6 @@ def trace_parameters_at_instant(self, formula_period):
             self.tracer,
         )
 
-    def _run_formula(self, variable, population, period):
-        """
-        Find the ``variable`` formula for the given ``period`` if it exists, and apply it to ``population``.
-        """
-
-        formula = variable.get_formula(period)
-        if formula is None:
-            return None
-
-        if self.trace:
-            parameters_at = self.trace_parameters_at_instant
-        else:
-            parameters_at = self.tax_benefit_system.get_parameters_at_instant
-
-        if formula.__code__.co_argcount == 2:
-            array = formula(population, period)
-        else:
-            array = formula(population, period, parameters_at)
-
-        return array
-
     def _check_period_consistency(self, period, variable):
         """
         Check that a period matches the variable definition_period
diff --git a/openfisca_core/simulations/simulation_builder.py b/openfisca_core/simulations/simulation_builder.py
index 41ca1e22e..71c37a352 100644
--- a/openfisca_core/simulations/simulation_builder.py
+++ b/openfisca_core/simulations/simulation_builder.py
@@ -1,8 +1,8 @@
-from typing import Dict, List, Iterable
+from typing import Dict, Iterable, List
 
 import copy
-import dpath.util
 
+import dpath.util
 import numpy
 
 from openfisca_core import periods
@@ -13,7 +13,7 @@
     VariableNotFoundError,
 )
 from openfisca_core.populations import Population
-from openfisca_core.simulations import helpers, Simulation
+from openfisca_core.simulations import Simulation, helpers
 from openfisca_core.variables import Variable
 
 
diff --git a/openfisca_core/simulations/tests/__init__.py b/openfisca_core/simulations/tests/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/openfisca_core/simulations/tests/test_run_formula.py b/openfisca_core/simulations/tests/test_run_formula.py
new file mode 100644
index 000000000..9b9486086
--- /dev/null
+++ b/openfisca_core/simulations/tests/test_run_formula.py
@@ -0,0 +1,81 @@
+from __future__ import annotations
+
+from numpy.typing import NDArray
+from openfisca_core.simulations.typing import (
+    Formula2,
+    Formula3,
+    Instant,
+    ParameterNodeAtInstant,
+    Params,
+    Population,
+)
+from typing import Any
+
+import numpy
+import pytest
+
+from openfisca_core import simulations
+
+
+class TestPopulation:
+    ...
+
+
+class TestInstant:
+    ...
+
+
+class TestParams:
+    def __call__(self, instant: Instant) -> ParameterNodeAtInstant:
+        ...
+
+
+@pytest.fixture
+def population() -> Population:
+    return TestPopulation()
+
+
+@pytest.fixture
+def instant() -> Instant:
+    return TestInstant()
+
+
+@pytest.fixture
+def params() -> Params:
+    return TestParams()
+
+
+def test_run_formula_without_formula(
+    population: Population, instant: Instant, params: Params
+) -> None:
+    """Test that RunFormula runs without a formula."""
+
+    run_formula = simulations.RunFormula(None)
+
+    assert not run_formula(population, instant, params)
+
+
+def test_run_formula_with_two_arguments(
+    population: Population, instant: Instant, params: Params
+) -> None:
+    """Test that RunFormula runs a formula with two arguments."""
+
+    def formula(a: Population, b: Instant) -> NDArray[Any]:
+        return numpy.array([1, 2, 3])
+
+    run_formula = simulations.RunFormula(formula)
+
+    assert run_formula(population, instant, params)
+
+
+def test_run_formula_with_three_arguments(
+    population: Population, instant: Instant, params: Params
+) -> None:
+    """Test that RunFormula runs a formula with three arguments."""
+
+    def formula(a: Population, b: Instant, c: Params) -> NDArray[Any]:
+        return numpy.array([1, 2, 3])
+
+    run_formula = simulations.RunFormula(formula)
+
+    assert run_formula(population, instant, params)
diff --git a/openfisca_core/simulations/typing.py b/openfisca_core/simulations/typing.py
new file mode 100644
index 000000000..cdca5a31d
--- /dev/null
+++ b/openfisca_core/simulations/typing.py
@@ -0,0 +1,37 @@
+from __future__ import annotations
+
+import abc
+from numpy.typing import NDArray
+from typing import Any, Protocol
+
+
+class Formula3(Protocol):
+    @abc.abstractmethod
+    def __call__(
+        self, __population: Population, __instant: Instant, __params: Params
+    ) -> NDArray[Any]:
+        ...
+
+
+class Formula2(Protocol):
+    @abc.abstractmethod
+    def __call__(self, __population: Population, __instant: Instant) -> NDArray[Any]:
+        ...
+
+
+class Instant(Protocol):
+    ...
+
+
+class ParameterNodeAtInstant(Protocol):
+    ...
+
+
+class Params(Protocol):
+    @abc.abstractmethod
+    def __call__(self, __instant: Instant) -> ParameterNodeAtInstant:
+        ...
+
+
+class Population(Protocol):
+    ...
diff --git a/openfisca_tasks/lint.mk b/openfisca_tasks/lint.mk
index a15b70457..2bf126682 100644
--- a/openfisca_tasks/lint.mk
+++ b/openfisca_tasks/lint.mk
@@ -60,6 +60,6 @@ lint-typing-strict-%:
 ## Run code formatters to correct style errors.
 format-style: $(shell git ls-files "*.py")
 	@$(call print_help,$@:)
-	@isort openfisca_core/periods
+	@isort openfisca_core/periods openfisca_core/simulations
 	@black $?
 	@$(call print_pass,$@:)