diff --git a/pyproject.toml b/pyproject.toml
index eedd227bee..5c9d205c87 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -361,6 +361,7 @@ module = [
   'aiida.cmdline.params.*',
   'aiida.common.*',
   'aiida.repository.*',
+  'aiida.schedulers.*',
   'aiida.tools.graph.*',
   'aiida.tools.query.*'
 ]
diff --git a/src/aiida/schedulers/datastructures.py b/src/aiida/schedulers/datastructures.py
index f3095e97a4..67982a100b 100644
--- a/src/aiida/schedulers/datastructures.py
+++ b/src/aiida/schedulers/datastructures.py
@@ -21,7 +21,9 @@
 import json
 from dataclasses import dataclass, field
 from datetime import datetime, timezone
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any, Literal
+
+from typing_extensions import Self
 
 from aiida.common import AIIDA_LOGGER, CodeRunMode
 from aiida.common.extendeddicts import AttributeDict, DefaultFieldsAttributeDict
@@ -78,16 +80,16 @@ class JobResource(DefaultFieldsAttributeDict, metaclass=abc.ABCMeta):
 
     @classmethod
     @abc.abstractmethod
-    def validate_resources(cls, **kwargs):
+    def validate_resources(cls, **kwargs: Any) -> dict[Any, Any] | None:
         """Validate the resources against the job resource class of this scheduler.
 
         :param kwargs: dictionary of values to define the job resources
         :raises ValueError: if the resources are invalid or incomplete
-        :return: optional tuple of parsed resource settings
+        :return: optional dict of parsed resource settings
         """
 
     @classmethod
-    def get_valid_keys(cls):
+    def get_valid_keys(cls) -> list[str]:
         """Return a list of valid keys to be passed to the constructor."""
         return list(cls._default_fields)
 
@@ -123,7 +125,7 @@ class NodeNumberJobResource(JobResource):
         num_cores_per_mpiproc: int
 
     @classmethod
-    def validate_resources(cls, **kwargs):
+    def validate_resources(cls, **kwargs: Any) -> AttributeDict:
         """Validate the resources against the job resource class of this scheduler.
 
         :param kwargs: dictionary of values to define the job resources
@@ -132,7 +134,7 @@ def validate_resources(cls, **kwargs):
         """
         resources = AttributeDict()
 
-        def is_greater_equal_one(parameter):
+        def is_greater_equal_one(parameter: str) -> None:
             value = getattr(resources, parameter, None)
             if value is not None and value < 1:
                 raise ValueError(f'`{parameter}` must be greater than or equal to one.')
@@ -176,7 +178,7 @@ def is_greater_equal_one(parameter):
 
         return resources
 
-    def __init__(self, **kwargs):
+    def __init__(self, **kwargs: Any):
         """Initialize the job resources from the passed arguments.
 
         :raises ValueError: if the resources are invalid or incomplete
@@ -185,16 +187,16 @@ def __init__(self, **kwargs):
         super().__init__(resources)
 
     @classmethod
-    def get_valid_keys(cls):
+    def get_valid_keys(cls) -> list[str]:
         """Return a list of valid keys to be passed to the constructor."""
         return super().get_valid_keys() + ['tot_num_mpiprocs']
 
     @classmethod
-    def accepts_default_mpiprocs_per_machine(cls):
+    def accepts_default_mpiprocs_per_machine(cls) -> Literal[True]:
         """Return True if this subclass accepts a `default_mpiprocs_per_machine` key, False otherwise."""
         return True
 
-    def get_tot_num_mpiprocs(self):
+    def get_tot_num_mpiprocs(self) -> int:
         """Return the total number of cpus of this job resource."""
         return self.num_machines * self.num_mpiprocs_per_machine
 
@@ -212,7 +214,7 @@ class ParEnvJobResource(JobResource):
         tot_num_mpiprocs: int
 
     @classmethod
-    def validate_resources(cls, **kwargs):
+    def validate_resources(cls, **kwargs: Any) -> AttributeDict:
         """Validate the resources against the job resource class of this scheduler.
 
         :param kwargs: dictionary of values to define the job resources
@@ -242,7 +244,7 @@ def validate_resources(cls, **kwargs):
 
         return resources
 
-    def __init__(self, **kwargs):
+    def __init__(self, **kwargs: Any):
         """Initialize the job resources from the passed arguments (the valid keys can be
         obtained with the function self.get_valid_keys()).
 
@@ -252,11 +254,11 @@ def __init__(self, **kwargs):
         super().__init__(resources)
 
     @classmethod
-    def accepts_default_mpiprocs_per_machine(cls):
+    def accepts_default_mpiprocs_per_machine(cls) -> Literal[False]:
         """Return True if this subclass accepts a `default_mpiprocs_per_machine` key, False otherwise."""
         return False
 
-    def get_tot_num_mpiprocs(self):
+    def get_tot_num_mpiprocs(self) -> int:
         """Return the total number of cpus of this job resource."""
         return self.tot_num_mpiprocs
 
@@ -569,7 +571,7 @@ class JobInfo(DefaultFieldsAttributeDict):
     }
 
     @staticmethod
-    def _serialize_job_state(job_state):
+    def _serialize_job_state(job_state: JobState) -> str:
         """Return the serialized value of the JobState instance."""
         if not isinstance(job_state, JobState):
             raise TypeError(f'invalid type for value {job_state}, should be an instance of `JobState`')
@@ -577,12 +579,12 @@ def _serialize_job_state(job_state):
         return job_state.value
 
     @staticmethod
-    def _deserialize_job_state(job_state):
+    def _deserialize_job_state(job_state: str) -> JobState:
         """Return an instance of JobState from the job_state string."""
         return JobState(job_state)
 
     @staticmethod
-    def _serialize_date(value):
+    def _serialize_date(value: datetime | None) -> dict[str, str | None] | None:
         """Serialise a data value
         :param value: The value to serialise
         :return: The serialised value
@@ -600,7 +602,7 @@ def _serialize_date(value):
         return {'date': value.astimezone(timezone.utc).strftime('%Y-%m-%dT%H:%M:%S.%f'), 'timezone': 'UTC'}
 
     @staticmethod
-    def _deserialize_date(value):
+    def _deserialize_date(value: dict[str, str] | None) -> datetime | None:
         """Deserialise a date
         :param value: The date vlue
         :return: The deserialised date
@@ -610,7 +612,7 @@ def _deserialize_date(value):
 
         if value['timezone'] is None:
             # naive date
-            return datetime.strptime(value['date'], '%Y-%m-%dT%H:%M:%S.%f')
+            return datetime.strptime(value['date'], '%Y-%m-%dT%H:%M:%S.%f')  # type: ignore[unreachable]
         if value['timezone'] == 'UTC':
             return make_aware(datetime.strptime(value['date'], '%Y-%m-%dT%H:%M:%S.%f'), timezone.utc)
 
@@ -620,7 +622,7 @@ def _deserialize_date(value):
         )
 
     @classmethod
-    def serialize_field(cls, value, field_type):
+    def serialize_field(cls, value: Any, field_type: str | None) -> Any:
         """Serialise a particular field value
 
         :param value: The value to serialise
@@ -635,7 +637,7 @@ def serialize_field(cls, value, field_type):
         return serializer_method(value)
 
     @classmethod
-    def deserialize_field(cls, value, field_type):
+    def deserialize_field(cls, value: Any, field_type: str | None) -> Any:
         """Deserialise the value of a particular field with a type
         :param value: The value
         :param field_type: The field type
@@ -648,14 +650,14 @@ def deserialize_field(cls, value, field_type):
 
         return deserializer_method(value)
 
-    def serialize(self):
+    def serialize(self) -> str:
         """Serialize the current data (as obtained by ``self.get_dict()``) into a JSON string.
 
         :return: A string with serialised representation of the current data.
         """
         return json.dumps(self.get_dict())
 
-    def get_dict(self):
+    def get_dict(self) -> dict[str, Any]:
         """Serialise the current data into a dictionary that is JSON-serializable.
 
         :return: A dictionary
@@ -663,7 +665,7 @@ def get_dict(self):
         return {k: self.serialize_field(v, self._special_serializers.get(k, None)) for k, v in self.items()}
 
     @classmethod
-    def load_from_dict(cls, data):
+    def load_from_dict(cls, data: dict[str, Any]) -> Self:
         """Create a new instance loading the values from serialised data in dictionary form
 
         :param data: The dictionary with the data to load from
@@ -674,7 +676,7 @@ def load_from_dict(cls, data):
         return instance
 
     @classmethod
-    def load_from_serialized(cls, data):
+    def load_from_serialized(cls, data: str) -> Self:
         """Create a new instance loading the values from JSON-serialised data as a string
 
         :param data: The string with the JSON-serialised data to load from
diff --git a/src/aiida/schedulers/plugins/pbsbaseclasses.py b/src/aiida/schedulers/plugins/pbsbaseclasses.py
index bcceeae19d..24921cf786 100644
--- a/src/aiida/schedulers/plugins/pbsbaseclasses.py
+++ b/src/aiida/schedulers/plugins/pbsbaseclasses.py
@@ -8,6 +8,8 @@
 ###########################################################################
 """Base classes for PBSPro and PBS/Torque plugins."""
 
+from __future__ import annotations
+
 import logging
 
 from aiida.common.escaping import escape_for_bash
@@ -118,8 +120,13 @@ class PbsBaseClass(BashCliScheduler):
     _map_status = _MAP_STATUS_PBS_COMMON
 
     def _get_resource_lines(
-        self, num_machines, num_mpiprocs_per_machine, num_cores_per_machine, max_memory_kb, max_wallclock_seconds
-    ):
+        self,
+        num_machines: int,
+        num_mpiprocs_per_machine: int | None,
+        num_cores_per_machine: int | None,
+        max_memory_kb: int | None,
+        max_wallclock_seconds: int | None,
+    ) -> list[str]:
         """Return a set a list of lines (possibly empty) with the header
         lines relative to:
 
diff --git a/src/aiida/schedulers/plugins/pbspro.py b/src/aiida/schedulers/plugins/pbspro.py
index 221b526254..d54ee11b62 100644
--- a/src/aiida/schedulers/plugins/pbspro.py
+++ b/src/aiida/schedulers/plugins/pbspro.py
@@ -10,6 +10,8 @@
 This has been tested on PBSPro v. 12.
 """
 
+from __future__ import annotations
+
 import logging
 
 from .pbsbaseclasses import PbsBaseClass
@@ -48,8 +50,13 @@ class PbsproScheduler(PbsBaseClass):
     # _map_status = _map_status_pbs_common
 
     def _get_resource_lines(
-        self, num_machines, num_mpiprocs_per_machine, num_cores_per_machine, max_memory_kb, max_wallclock_seconds
-    ):
+        self,
+        num_machines: int,
+        num_mpiprocs_per_machine: int | None,
+        num_cores_per_machine: int | None,
+        max_memory_kb: int | None,
+        max_wallclock_seconds: int | None,
+    ) -> list[str]:
         """Return the lines for machines, memory and wallclock relative
         to pbspro.
         """
diff --git a/src/aiida/schedulers/plugins/torque.py b/src/aiida/schedulers/plugins/torque.py
index b2ca36d64b..0d2fe56f09 100644
--- a/src/aiida/schedulers/plugins/torque.py
+++ b/src/aiida/schedulers/plugins/torque.py
@@ -10,6 +10,8 @@
 This has been tested on Torque v.2.4.16 (from Ubuntu).
 """
 
+from __future__ import annotations
+
 import logging
 
 from .pbsbaseclasses import PbsBaseClass
@@ -42,8 +44,13 @@ class TorqueScheduler(PbsBaseClass):
     # _map_status = _map_status_pbs_common
 
     def _get_resource_lines(
-        self, num_machines, num_mpiprocs_per_machine, num_cores_per_machine, max_memory_kb, max_wallclock_seconds
-    ):
+        self,
+        num_machines: int,
+        num_mpiprocs_per_machine: int | None,
+        num_cores_per_machine: int | None,
+        max_memory_kb: int | None,
+        max_wallclock_seconds: int | None,
+    ) -> list[str]:
         """Return the lines for machines, memory and wallclock relative
         to pbspro.
         """
diff --git a/src/aiida/schedulers/scheduler.py b/src/aiida/schedulers/scheduler.py
index 08cc74023a..b664c98c0f 100644
--- a/src/aiida/schedulers/scheduler.py
+++ b/src/aiida/schedulers/scheduler.py
@@ -49,11 +49,15 @@ class Scheduler(metaclass=abc.ABCMeta):
     # The class to be used for the job resource.
     _job_resource_class: t.Type[JobResource] | None = None
 
-    def __str__(self):
+    def __init__(self) -> None:
+        assert self._job_resource_class is not None and issubclass(self._job_resource_class, JobResource)
+        self._transport: Transport | None = None
+
+    def __str__(self) -> str:
         return self.__class__.__name__
 
     @classmethod
-    def preprocess_resources(cls, resources: dict[str, t.Any], default_mpiprocs_per_machine: int | None = None):
+    def preprocess_resources(cls, resources: dict[str, t.Any], default_mpiprocs_per_machine: int | None = None) -> None:
         """Pre process the resources.
 
         Add the `num_mpiprocs_per_machine` key to the `resources` if it is not already defined and it cannot be deduced
@@ -73,7 +77,7 @@ class of this scheduler does not accept the `num_mpiprocs_per_machine` keyword.
             resources['num_mpiprocs_per_machine'] = default_mpiprocs_per_machine
 
     @classmethod
-    def validate_resources(cls, **resources):
+    def validate_resources(cls, **resources: t.Any) -> None:
         """Validate the resources against the job resource class of this scheduler.
 
         :param resources: keyword arguments to define the job resources
@@ -82,12 +86,8 @@ def validate_resources(cls, **resources):
         assert cls._job_resource_class is not None and issubclass(cls._job_resource_class, JobResource)
         cls._job_resource_class.validate_resources(**resources)
 
-    def __init__(self):
-        assert self._job_resource_class is not None and issubclass(self._job_resource_class, JobResource)
-        self._transport = None
-
     @classmethod
-    def get_short_doc(cls):
+    def get_short_doc(cls) -> str:
         """Return the first non-empty line of the class docstring, if available."""
         # Remove empty lines
         docstring = cls.__doc__
@@ -107,7 +107,7 @@ def get_feature(self, feature_name: str) -> bool:
             raise NotImplementedError(f'Feature {feature_name} not implemented for this scheduler')
 
     @property
-    def logger(self):
+    def logger(self) -> log.AiidaLoggerType:
         """Return the internal logger."""
         try:
             return self._logger
@@ -120,7 +120,7 @@ def job_resource_class(cls) -> t.Type[JobResource]:  # noqa: N805
         return cls._job_resource_class
 
     @classmethod
-    def create_job_resource(cls, **kwargs):
+    def create_job_resource(cls, **kwargs: t.Any) -> JobResource:
         """Create a suitable job resource from the kwargs specified."""
         assert cls._job_resource_class is not None and issubclass(cls._job_resource_class, JobResource)
         return cls._job_resource_class(**kwargs)
@@ -374,14 +374,14 @@ def get_detailed_job_info(self, job_id: str) -> dict[str, str | int]:
         return detailed_job_info
 
     @property
-    def transport(self):
+    def transport(self) -> Transport:
         """Return the transport set for this scheduler."""
         if self._transport is None:
             raise SchedulerError('Use the set_transport function to set the transport for the scheduler first.')
 
         return self._transport
 
-    def set_transport(self, transport: Transport):
+    def set_transport(self, transport: Transport) -> None:
         """Set the transport to be used to query the machine or to submit scripts.
 
         This class assumes that the transport is open and active.