diff --git a/src/blenderbim/blenderbim/core/cost.py b/src/blenderbim/blenderbim/core/cost.py
index f23cb60a49..0859ed59b1 100644
--- a/src/blenderbim/blenderbim/core/cost.py
+++ b/src/blenderbim/blenderbim/core/cost.py
@@ -289,7 +289,7 @@ def calculate_cost_item_resource_value(ifc: tool.Ifc, cost_item: ifcopenshell.en
     ifc.run("cost.calculate_cost_item_resource_value", cost_item=cost_item)
 
 
-def export_cost_schedules(cost: tool.Cost, filepath, format, cost_schedule=None):
+def export_cost_schedules(cost: tool.Cost, filepath: str, format: str, cost_schedule=None):
     cost.play_sound()
     return cost.export_cost_schedules(filepath, format, cost_schedule)
 
diff --git a/src/blenderbim/blenderbim/tool/cost.py b/src/blenderbim/blenderbim/tool/cost.py
index aa4bb8264c..5d4698a24f 100644
--- a/src/blenderbim/blenderbim/tool/cost.py
+++ b/src/blenderbim/blenderbim/tool/cost.py
@@ -529,7 +529,7 @@ class Cost(blenderbim.core.tool.Cost):
         props.is_cost_update_enabled = True
 
     @classmethod
-    def export_cost_schedules(cls, filepath, format=None, cost_schedule=None):
+    def export_cost_schedules(cls, filepath: str, format: str, cost_schedule=None):
         import subprocess
         import os
         import sys
@@ -642,7 +642,7 @@ class Cost(blenderbim.core.tool.Cost):
         return bool(cost_items)
 
     @classmethod
-    def load_product_cost_items(cls, product):
+    def load_product_cost_items(cls, product: ifcopenshell.entity_instance) -> None:
         props = bpy.context.scene.BIMCostProperties
         props.is_cost_update_enabled = False
         props.product_cost_items.clear()
diff --git a/src/ifc5d/ifc5d/csv2ifc.py b/src/ifc5d/ifc5d/csv2ifc.py
index 3bdaa0d93c..218a257d48 100644
--- a/src/ifc5d/ifc5d/csv2ifc.py
+++ b/src/ifc5d/ifc5d/csv2ifc.py
@@ -212,7 +212,7 @@ class Csv2Ifc:
 
         self.create_cost_items(cost_item["children"], cost_item["ifc"])
 
-    def create_unit(self, symbol) -> ifcopenshell.entity_instance:
+    def create_unit(self, symbol: str) -> ifcopenshell.entity_instance:
         unit = self.units.get(symbol, None)
         if unit:
             return unit
@@ -227,7 +227,7 @@ class Csv2Ifc:
         ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcProject")
 
 
-def has_property(self, product, property_name) -> bool:
+def has_property(self, product: ifcopenshell.entity_instance, property_name: str) -> bool:
     if not property_name:
         return True
     qtos = ifcopenshell.util.element.get_psets(product, qtos_only=True)
diff --git a/src/ifc5d/ifc5d/ifc5Dspreadsheet.py b/src/ifc5d/ifc5d/ifc5Dspreadsheet.py
index 8e2b739cbb..826f610817 100644
--- a/src/ifc5d/ifc5d/ifc5Dspreadsheet.py
+++ b/src/ifc5d/ifc5d/ifc5Dspreadsheet.py
@@ -26,13 +26,18 @@ import ifcopenshell
 import ifcopenshell.util.element
 import ifcopenshell.util.cost
 import ifcopenshell.util.date
+from typing import Union, Optional
 
 
 class IfcDataGetter:
     @staticmethod
-    def get_schedules(file, filter_by_schedule=None):
+    def get_schedules(
+        file: ifcopenshell.file, filter_by_schedule: Optional[ifcopenshell.entity_instance] = None
+    ) -> list[ifcopenshell.entity_instance]:
         return [
-            schedule for schedule in file.by_type("IfcCostSchedule") if not filter_by_schedule or schedule == filter_by_schedule
+            schedule
+            for schedule in file.by_type("IfcCostSchedule")
+            if not filter_by_schedule or schedule == filter_by_schedule
         ]
 
     @staticmethod
@@ -195,7 +200,18 @@ class IfcDataGetter:
 
 
 class Ifc5Dwriter:
-    def __init__(self, file=None, output=None, cost_schedule=None):
+    file: ifcopenshell.file
+
+    def __init__(
+        self,
+        file: Union[str, ifcopenshell.file],
+        output: str,
+        cost_schedule: Optional[ifcopenshell.entity_instance] = None,
+    ):
+        """
+        Args:
+            cost_schedule: exported cost schedule. If not provided, will export all available schedules.
+        """
         self.output = output
         if isinstance(file, str):
             self.file = ifcopenshell.open(file)
diff --git a/src/ifcopenshell-python/ifcopenshell/api/cost/add_cost_item_quantity.py b/src/ifcopenshell-python/ifcopenshell/api/cost/add_cost_item_quantity.py
index 61ba86f6b2..fd1d793300 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/cost/add_cost_item_quantity.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/cost/add_cost_item_quantity.py
@@ -17,10 +17,13 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import ifcopenshell.api
+import ifcopenshell.util.unit
 
 
 def add_cost_item_quantity(
-    file: ifcopenshell.file, cost_item: ifcopenshell.entity_instance, ifc_class: str = "IfcQuantityCount"
+    file: ifcopenshell.file,
+    cost_item: ifcopenshell.entity_instance,
+    ifc_class: ifcopenshell.util.unit.QUANTITY_CLASS = "IfcQuantityCount",
 ) -> ifcopenshell.entity_instance:
     """Adds a new quantity associated with a cost item
 
diff --git a/src/ifcopenshell-python/ifcopenshell/api/cost/assign_cost_item_quantity.py b/src/ifcopenshell-python/ifcopenshell/api/cost/assign_cost_item_quantity.py
index ae0643acae..d9ef5c61f6 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/cost/assign_cost_item_quantity.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/cost/assign_cost_item_quantity.py
@@ -17,14 +17,14 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import ifcopenshell.api
-from typing import Optional
+from typing import Any
 
 
 def assign_cost_item_quantity(
     file: ifcopenshell.file,
     cost_item: ifcopenshell.entity_instance,
     products: list[ifcopenshell.entity_instance],
-    prop_name: Optional[str] = "",
+    prop_name: str = "",
 ) -> None:
     """Adds a cost item quantity that is parametrically connected to a product
 
@@ -96,6 +96,9 @@ def assign_cost_item_quantity(
 
 
 class Usecase:
+    file: ifcopenshell.file
+    settings: dict[str, Any]
+
     def execute(self):
         if self.settings["prop_name"]:
             self.quantities = set(self.settings["cost_item"].CostQuantities or [])
@@ -113,7 +116,9 @@ class Usecase:
         else:
             self.update_cost_item_count()
 
-    def assign_cost_control(self, related_object, cost_item):
+    def assign_cost_control(
+        self, related_object: ifcopenshell.entity_instance, cost_item: ifcopenshell.entity_instance
+    ) -> ifcopenshell.entity_instance:
         return ifcopenshell.api.run(
             "control.assign_control",
             self.file,
@@ -121,12 +126,12 @@ class Usecase:
             relating_control=cost_item,
         )
 
-    def add_quantity_from_related_object(self, element):
+    def add_quantity_from_related_object(self, element: ifcopenshell.entity_instance) -> None:
         for relationship in element.IsDefinedBy:
             if relationship.is_a("IfcRelDefinesByProperties"):
                 self.add_quantity_from_qto(relationship.RelatingPropertyDefinition)
 
-    def add_quantity_from_qto(self, qto):
+    def add_quantity_from_qto(self, qto: ifcopenshell.entity_instance) -> None:
         if not qto.is_a("IfcElementQuantity"):
             return
         for prop in qto.Quantities:
diff --git a/src/ifcopenshell-python/ifcopenshell/util/unit.py b/src/ifcopenshell-python/ifcopenshell/util/unit.py
index fdbee952a4..55eda62d82 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/unit.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/unit.py
@@ -337,6 +337,25 @@ unit_symbols = {
     "fahrenheit": "°F",
 }
 
+QUANTITY_CLASS = Literal[
+    "IfcQuantityCount",
+    "IfcQuantityNumber",
+    "IfcQuantityLength",
+    "IfcQuantityArea",
+    "IfcQuantityVolume",
+    "IfcQuantityWeight",
+    "IfcQuantityTime",
+    "IfcQuantityCount",
+]
+
+MEASURE_CLASS = Literal[
+    "IfcNumericMeasure",
+    "IfcLengthMeasure",
+    "IfcAreaMeasure",
+    "IfcVolumeMeasure",
+    "IfcMassMeasure",
+]
+
 
 def get_prefix(text):
     if text:
@@ -468,14 +487,14 @@ def get_property_unit(
         return units[0]
 
 
-def get_unit_measure_class(unit_type: str) -> str:
+def get_unit_measure_class(unit_type: str) -> MEASURE_CLASS:
     if unit_type == "USERDEFINED":
         # See https://github.com/buildingSMART/IFC4.3.x-development/issues/71
         return "IfcNumericMeasure"
     return "Ifc" + unit_type[0:-4].lower().capitalize() + "Measure"
 
 
-def get_measure_unit_type(measure_class: str) -> str:
+def get_measure_unit_type(measure_class: MEASURE_CLASS) -> str:
     if measure_class == "IfcNumericMeasure":
         # See https://github.com/buildingSMART/IFC4.3.x-development/issues/71
         return "USERDEFINED"
@@ -484,7 +503,7 @@ def get_measure_unit_type(measure_class: str) -> str:
     return measure_class.upper() + "UNIT"
 
 
-def get_symbol_measure_class(symbol: Optional[str] = None) -> str:
+def get_symbol_measure_class(symbol: Optional[str] = None) -> MEASURE_CLASS:
     # Dumb, but everybody gets it, unlike regex golf
     if not symbol:
         return "IfcNumericMeasure"
@@ -502,7 +521,7 @@ def get_symbol_measure_class(symbol: Optional[str] = None) -> str:
     return "IfcNumericMeasure"
 
 
-def get_symbol_quantity_class(symbol: Optional[str] = None) -> str:
+def get_symbol_quantity_class(symbol: Optional[str] = None) -> QUANTITY_CLASS:
     # Dumb, but everybody gets it, unlike regex golf
     if not symbol:
         return "IfcQuantityCount"