diff --git a/tests/test_io.py b/tests/test_io.py
index a2c25ab4..737517b8 100644
--- a/tests/test_io.py
+++ b/tests/test_io.py
@@ -5,6 +5,7 @@
 import pytest
 import torch
 from ase import Atoms
+from ase.build import molecule
 from phonopy.structure.atoms import PhonopyAtoms
 from pymatgen.core import Structure
 
@@ -88,6 +89,69 @@ def test_multiple_atoms_to_state(si_atoms: Atoms) -> None:
     )
 
 
+@pytest.mark.parametrize(
+    ("charge", "spin", "expected_charge", "expected_spin"),
+    [
+        (1.0, 1.0, 1.0, 1.0),  # Non-zero charge and spin
+        (0.0, 0.0, 0.0, 0.0),  # Explicit zero charge and spin
+        (None, None, 0.0, 0.0),  # No charge/spin set, defaults to zero
+    ],
+)
+def test_atoms_to_state_with_charge_spin(
+    charge: float | None,
+    spin: float | None,
+    expected_charge: float,
+    expected_spin: float,
+) -> None:
+    """Test conversion from ASE Atoms with charge and spin to state tensors."""
+    mol = molecule("H2O")
+    if charge is not None:
+        mol.info["charge"] = charge
+    if spin is not None:
+        mol.info["spin"] = spin
+
+    state = ts.io.atoms_to_state([mol], DEVICE, DTYPE)
+
+    # Check basic properties
+    assert isinstance(state, SimState)
+    assert state.charge is not None
+    assert state.spin is not None
+    assert state.charge.shape == (1,)
+    assert state.spin.shape == (1,)
+    assert state.charge[0].item() == expected_charge
+    assert state.spin[0].item() == expected_spin
+
+
+def test_multiple_atoms_to_state_with_charge_spin() -> None:
+    """Test conversion from multiple ASE Atoms with different charge/spin values."""
+    mol1 = molecule("H2O")
+    mol1.info["charge"] = 1.0
+    mol1.info["spin"] = 1.0
+
+    mol2 = molecule("CH4")
+    mol2.info["charge"] = -1.0
+    mol2.info["spin"] = 0.0
+
+    mol3 = molecule("NH3")
+    mol3.info["charge"] = 0.0
+    mol3.info["spin"] = 2.0
+
+    state = ts.io.atoms_to_state([mol1, mol2, mol3], DEVICE, DTYPE)
+
+    # Check basic properties
+    assert isinstance(state, SimState)
+    assert state.charge is not None
+    assert state.spin is not None
+    assert state.charge.shape == (3,)
+    assert state.spin.shape == (3,)
+    assert state.charge[0].item() == 1.0
+    assert state.charge[1].item() == -1.0
+    assert state.charge[2].item() == 0.0
+    assert state.spin[0].item() == 1.0
+    assert state.spin[1].item() == 0.0
+    assert state.spin[2].item() == 2.0
+
+
 def test_state_to_structure(ar_supercell_sim_state: SimState) -> None:
     """Test conversion from state tensors to list of pymatgen Structure."""
     structures = ts.io.state_to_structures(ar_supercell_sim_state)
@@ -114,6 +178,23 @@ def test_state_to_atoms(ar_supercell_sim_state: SimState) -> None:
     assert len(atoms[0]) == 32
 
 
+def test_state_to_atoms_with_charge_spin() -> None:
+    """Test conversion from state with charge/spin to ASE Atoms preserves charge/spin."""
+    mol = molecule("H2O")
+    mol.info["charge"] = 1.0
+    mol.info["spin"] = 1.0
+
+    state = ts.io.atoms_to_state([mol], DEVICE, DTYPE)
+    atoms = ts.io.state_to_atoms(state)
+
+    assert len(atoms) == 1
+    assert isinstance(atoms[0], Atoms)
+    assert "charge" in atoms[0].info
+    assert "spin" in atoms[0].info
+    assert atoms[0].info["charge"] == 1
+    assert atoms[0].info["spin"] == 1
+
+
 def test_state_to_multiple_atoms(ar_double_sim_state: SimState) -> None:
     """Test conversion from state tensors to list of ASE Atoms."""
     atoms = ts.io.state_to_atoms(ar_double_sim_state)
@@ -253,6 +334,9 @@ def test_state_round_trip(
         # since both use their own isotope masses based on species,
         # not the ones in the state
         assert torch.allclose(sim_state.masses, round_trip_state.masses)
+        # Check charge/spin round trip
+        assert torch.allclose(sim_state.charge, round_trip_state.charge)
+        assert torch.allclose(sim_state.spin, round_trip_state.spin)
 
 
 def test_state_to_atoms_importerror(monkeypatch: pytest.MonkeyPatch) -> None:
diff --git a/torch_sim/models/interface.py b/torch_sim/models/interface.py
index 5c6a243a..dbcd4448 100644
--- a/torch_sim/models/interface.py
+++ b/torch_sim/models/interface.py
@@ -200,7 +200,7 @@ def validate_model_outputs(  # noqa: C901, PLR0915
         This validator creates small test systems (silicon and iron) for validation.
         It tests both single and multi-batch processing capabilities.
     """
-    from ase.build import bulk
+    from ase.build import bulk, molecule
 
     for attr in ("dtype", "device", "compute_stress", "compute_forces"):
         if not hasattr(model, attr):
@@ -229,6 +229,8 @@ def validate_model_outputs(  # noqa: C901, PLR0915
     og_cell = sim_state.cell.clone()
     og_system_idx = sim_state.system_idx.clone()
     og_atomic_nums = sim_state.atomic_numbers.clone()
+    og_charge = sim_state.charge.clone()
+    og_spin = sim_state.spin.clone()
 
     model_output = model.forward(sim_state)
 
@@ -241,6 +243,10 @@ def validate_model_outputs(  # noqa: C901, PLR0915
         raise ValueError(f"{og_system_idx=} != {sim_state.system_idx=}")
     if not torch.allclose(og_atomic_nums, sim_state.atomic_numbers):
         raise ValueError(f"{og_atomic_nums=} != {sim_state.atomic_numbers=}")
+    if not torch.allclose(og_charge, sim_state.charge):
+        raise ValueError(f"{og_charge=} != {sim_state.charge=}")
+    if not torch.allclose(og_spin, sim_state.spin):
+        raise ValueError(f"{og_spin=} != {sim_state.spin=}")
 
     # assert model output has the correct keys
     if "energy" not in model_output:
@@ -300,3 +306,43 @@ def validate_model_outputs(  # noqa: C901, PLR0915
         raise ValueError(f"{fe_model_output['forces'].shape=} != (12, 3)")
     if stress_computed and fe_model_output["stress"].shape != (1, 3, 3):
         raise ValueError(f"{fe_model_output['stress'].shape=} != (1, 3, 3)")
+
+    # Test that models can handle non-zero charge and spin
+    benzene_atoms = molecule("C6H6")
+    benzene_atoms.info["charge"] = 1.0
+    benzene_atoms.info["spin"] = 1.0
+    charged_state = ts.io.atoms_to_state([benzene_atoms], device, dtype)
+
+    # Ensure state has charge/spin before testing model
+    if charged_state.charge is None or charged_state.spin is None:
+        raise ValueError(
+            "atoms_to_state did not extract charge/spin. "
+            "Cannot test model charge/spin handling."
+        )
+
+    # Test that model can handle charge/spin without crashing
+    og_charged_charge = charged_state.charge.clone()
+    og_charged_spin = charged_state.spin.clone()
+    try:
+        charged_output = model.forward(charged_state)
+    except Exception as e:
+        raise ValueError(
+            "Model failed to handle non-zero charge/spin. "
+            "Models must be able to process states with charge and spin values. "
+        ) from e
+
+    # Verify model didn't mutate charge/spin
+    if not torch.allclose(og_charged_charge, charged_state.charge):
+        raise ValueError(
+            f"Model mutated charge: {og_charged_charge=} != {charged_state.charge=}"
+        )
+    if not torch.allclose(og_charged_spin, charged_state.spin):
+        raise ValueError(
+            f"Model mutated spin: {og_charged_spin=} != {charged_state.spin=}"
+        )
+    # Verify output shape is still correct
+    if charged_output["energy"].shape != (1,):
+        raise ValueError(
+            f"energy shape incorrect with charge/spin: "
+            f"{charged_output['energy'].shape=} != (1,)"
+        )