diff --git a/oidc-controller/api/routers/oidc.py b/oidc-controller/api/routers/oidc.py
index 808f8cad..dc42807a 100644
--- a/oidc-controller/api/routers/oidc.py
+++ b/oidc-controller/api/routers/oidc.py
@@ -34,6 +34,8 @@
 from ..routers.socketio import connections_reload, sio
 
 from ..verificationConfigs.crud import VerificationConfigCRUD
+from ..verificationConfigs.helpers import VariableSubstitutionError
+
 
 ChallengePollUri = "/poll"
 AuthorizeCallbackUri = "/callback"
@@ -125,7 +127,19 @@ async def get_authorize(request: Request, db: Database = Depends(get_db)):
     ver_config = await VerificationConfigCRUD(db).get(ver_config_id)
 
     # Create presentation_request to show on screen
-    response = client.create_presentation_request(ver_config.generate_proof_request())
+    try:
+        response = client.create_presentation_request(
+            ver_config.generate_proof_request()
+        )
+    except VariableSubstitutionError as e:
+        return JSONResponse(
+            status_code=http_status.HTTP_400_BAD_REQUEST,
+            content={
+                "detail": f"Variable substitution error: \
+'{e.variable_name}' not found in substitution map."
+            },
+        )
+
     pres_exch_dict = response.dict()
 
     # Prepeare the presentation request
diff --git a/oidc-controller/api/verificationConfigs/helpers.py b/oidc-controller/api/verificationConfigs/helpers.py
new file mode 100644
index 00000000..a60de98b
--- /dev/null
+++ b/oidc-controller/api/verificationConfigs/helpers.py
@@ -0,0 +1,43 @@
+from .variableSubstitutions import variable_substitution_map
+
+
+class VariableSubstitutionError(Exception):
+    """Custom exception for if a variable is used that does not exist."""
+
+    def __init__(self, variable_name: str):
+        self.variable_name = variable_name
+        super().__init__(f"Variable '{variable_name}' not found in substitution map.")
+
+
+def replace_proof_variables(proof_req_dict: dict) -> dict:
+    """
+    Recursively replaces variables in the proof request with actual values.
+    The map is provided by imported variable_substitution_map.
+    Additional variables can be added to the map in the variableSubstitutions.py file,
+    or other dynamic functionality.
+
+    Args:
+        proof_req_dict (dict): The proof request dictionary from the resolved config.
+
+    Returns:
+        dict: The updated proof request dictionary with placeholder variables replaced.
+    """
+
+    for k, v in proof_req_dict.items():
+        # If the value is a dictionary, recurse
+        if isinstance(v, dict):
+            replace_proof_variables(v)
+        # If the value is a list, iterate trhough list items and recurse
+        elif isinstance(v, list):
+            for i in v:
+                if isinstance(i, dict):
+                    replace_proof_variables(i)
+        # If the value is a string and matches a key in the map, replace it
+        elif isinstance(v, str) and v.startswith("$"):
+            if v in variable_substitution_map:
+                proof_req_dict[k] = variable_substitution_map[v]()
+            else:
+                raise VariableSubstitutionError(v)
+
+        # Base case: If the value is not a dict, list, or matching string, do nothing
+    return proof_req_dict
diff --git a/oidc-controller/api/verificationConfigs/models.py b/oidc-controller/api/verificationConfigs/models.py
index fd5e92ed..2652d3a7 100644
--- a/oidc-controller/api/verificationConfigs/models.py
+++ b/oidc-controller/api/verificationConfigs/models.py
@@ -4,6 +4,7 @@
 
 from .examples import ex_ver_config
 from ..core.config import settings
+from .helpers import replace_proof_variables
 
 
 # Slightly modified from ACAPY models.
@@ -44,6 +45,9 @@ class VerificationConfigBase(BaseModel):
     generate_consistent_identifier: Optional[bool] = Field(default=False)
     include_v1_attributes: Optional[bool] = Field(default=False)
 
+    def get_now(self) -> int:
+        return int(time.time())
+
     def generate_proof_request(self):
         result = {
             "name": "proof_requested",
@@ -61,15 +65,16 @@ def generate_proof_request(self):
                     "from": int(time.time()),
                     "to": int(time.time()),
                 }
-        # TODO add I indexing
-        for req_pred in self.proof_request.requested_predicates:
+        for i, req_pred in enumerate(self.proof_request.requested_predicates):
             label = req_pred.label or "req_pred_" + str(i)
             result["requested_predicates"][label] = req_pred.dict(exclude_none=True)
             if settings.SET_NON_REVOKED:
-                result["requested_attributes"][label]["non_revoked"] = {
+                result["requested_predicates"][label]["non_revoked"] = {
                     "from": int(time.time()),
                     "to": int(time.time()),
                 }
+        # Recursively check for subistitution variables and invoke replacement function
+        result = replace_proof_variables(result)
         return result
 
     model_config = ConfigDict(json_schema_extra={"example": ex_ver_config})
diff --git a/oidc-controller/api/verificationConfigs/tests/test_helpers.py b/oidc-controller/api/verificationConfigs/tests/test_helpers.py
new file mode 100644
index 00000000..236f1b87
--- /dev/null
+++ b/oidc-controller/api/verificationConfigs/tests/test_helpers.py
@@ -0,0 +1,66 @@
+import pytest
+from unittest.mock import patch
+from api.verificationConfigs.helpers import (
+    replace_proof_variables,
+    VariableSubstitutionError,
+)
+
+# Mock variable substitution map
+mock_variable_substitution_map = {"$var1": lambda: "value1", "$var2": lambda: "value2"}
+
+
+@patch(
+    "api.verificationConfigs.helpers.variable_substitution_map",
+    mock_variable_substitution_map,
+)
+def test_replace_proof_variables_empty_dict():
+    assert replace_proof_variables({}) == {}
+
+
+@patch(
+    "api.verificationConfigs.helpers.variable_substitution_map",
+    mock_variable_substitution_map,
+)
+def test_replace_proof_variables_no_variables():
+    input_dict = {"key1": "value1", "key2": "value2"}
+    assert replace_proof_variables(input_dict) == input_dict
+
+
+@patch(
+    "api.verificationConfigs.helpers.variable_substitution_map",
+    mock_variable_substitution_map,
+)
+def test_replace_proof_variables_with_variables():
+    input_dict = {"key1": "$var1", "key2": "$var2"}
+    expected_dict = {"key1": "value1", "key2": "value2"}
+    assert replace_proof_variables(input_dict) == expected_dict
+
+
+@patch(
+    "api.verificationConfigs.helpers.variable_substitution_map",
+    mock_variable_substitution_map,
+)
+def test_replace_proof_variables_variable_not_found():
+    input_dict = {"key1": "$var3"}
+    with pytest.raises(VariableSubstitutionError):
+        replace_proof_variables(input_dict)
+
+
+@patch(
+    "api.verificationConfigs.helpers.variable_substitution_map",
+    mock_variable_substitution_map,
+)
+def test_replace_proof_variables_nested_dict():
+    input_dict = {"key1": {"key2": "$var1"}}
+    expected_dict = {"key1": {"key2": "value1"}}
+    assert replace_proof_variables(input_dict) == expected_dict
+
+
+@patch(
+    "api.verificationConfigs.helpers.variable_substitution_map",
+    mock_variable_substitution_map,
+)
+def test_replace_proof_variables_list():
+    input_dict = {"key1": [{"key2": "$var2"}]}
+    expected_dict = {"key1": [{"key2": "value2"}]}
+    assert replace_proof_variables(input_dict) == expected_dict
diff --git a/oidc-controller/api/verificationConfigs/tests/test_variable_substitutions.py b/oidc-controller/api/verificationConfigs/tests/test_variable_substitutions.py
new file mode 100644
index 00000000..ae6c7056
--- /dev/null
+++ b/oidc-controller/api/verificationConfigs/tests/test_variable_substitutions.py
@@ -0,0 +1,60 @@
+import time
+import pytest
+from datetime import datetime, timedelta
+from api.verificationConfigs.variableSubstitutions import VariableSubstitutionMap
+
+
+def test_get_now():
+    vsm = VariableSubstitutionMap()
+    assert abs(vsm.get_now() - int(time.time())) < 2  # Allowing a small time difference
+
+
+def test_get_today_date():
+    vsm = VariableSubstitutionMap()
+    assert vsm.get_today_date() == datetime.today().strftime("%Y%m%d")
+
+
+def test_get_tomorrow_date():
+    vsm = VariableSubstitutionMap()
+    assert vsm.get_tomorrow_date() == (datetime.today() + timedelta(days=1)).strftime(
+        "%Y%m%d"
+    )
+
+
+def test_get_threshold_years_date():
+    vsm = VariableSubstitutionMap()
+    years = 5
+    expected_date = (
+        datetime.today().replace(year=datetime.today().year - years).strftime("%Y%m%d")
+    )
+    assert vsm.get_threshold_years_date(years) == int(expected_date)
+
+
+def test_contains_static_variable():
+    vsm = VariableSubstitutionMap()
+    assert "$now" in vsm
+    assert "$today_str" in vsm
+    assert "$tomorrow_str" in vsm
+
+
+def test_contains_dynamic_variable():
+    vsm = VariableSubstitutionMap()
+    assert "$threshold_years_5" in vsm
+
+
+def test_getitem_static_variable():
+    vsm = VariableSubstitutionMap()
+    assert callable(vsm["$now"])
+    assert callable(vsm["$today_str"])
+    assert callable(vsm["$tomorrow_str"])
+
+
+def test_getitem_dynamic_variable():
+    vsm = VariableSubstitutionMap()
+    assert callable(vsm["$threshold_years_5"])
+
+
+def test_getitem_key_error():
+    vsm = VariableSubstitutionMap()
+    with pytest.raises(KeyError):
+        vsm["$non_existent_key"]
diff --git a/oidc-controller/api/verificationConfigs/variableSubstitutions.py b/oidc-controller/api/verificationConfigs/variableSubstitutions.py
new file mode 100644
index 00000000..c044112b
--- /dev/null
+++ b/oidc-controller/api/verificationConfigs/variableSubstitutions.py
@@ -0,0 +1,78 @@
+"""
+This file contains VariableSubstitutionMap class, which provides a mapping of
+static variables that can be used in a proof.
+Other users of this project can add their own variable substitutions or override
+the entire file to suit their own needs.
+"""
+
+from datetime import datetime, timedelta
+import time
+import re
+
+
+class VariableSubstitutionMap:
+    def __init__(self):
+        # Map of static variables that can be used in a proof
+        # This class defines threshold_years_X as a dynamic one
+        self.static_map = {
+            "$now": self.get_now,
+            "$today_str": self.get_today_date,
+            "$tomorrow_str": self.get_tomorrow_date,
+        }
+
+    def get_threshold_years_date(self, years: int) -> int:
+        """
+        Calculate the threshold date for a given number of years.
+
+        Args:
+            years (int): The number of years to subtract from the current year.
+
+        Returns:
+            int: The current date minux X years in YYYYMMDD format.
+        """
+        threshold_date = datetime.today().replace(year=datetime.today().year - years)
+        return int(threshold_date.strftime("%Y%m%d"))
+
+    def get_now(self) -> int:
+        """
+        Get the current timestamp.
+
+        Returns:
+            int: The current timestamp in seconds since the epoch.
+        """
+        return int(time.time())
+
+    def get_today_date(self) -> str:
+        """
+        Get today's date in YYYYMMDD format.
+
+        Returns:
+            str: Today's date in YYYYMMDD format.
+        """
+        return datetime.today().strftime("%Y%m%d")
+
+    def get_tomorrow_date(self) -> str:
+        """
+        Get tomorrow's date in YYYYMMDD format.
+
+        Returns:
+            str: Tomorrow's date in YYYYMMDD format.
+        """
+        return (datetime.today() + timedelta(days=1)).strftime("%Y%m%d")
+
+    # For "dynamic" variables, use a regex to match the key and return a lambda function
+    # So a proof request can use $threshold_years_X to get the years back for X years
+    def __contains__(self, key: str) -> bool:
+        return key in self.static_map or re.match(r"\$threshold_years_(\d+)", key)
+
+    def __getitem__(self, key: str):
+        if key in self.static_map:
+            return self.static_map[key]
+        match = re.match(r"\$threshold_years_(\d+)", key)
+        if match:
+            return lambda: self.get_threshold_years_date(int(match.group(1)))
+        raise KeyError(f"Key {key} not found in format_args_function_map")
+
+
+# Create an instance of the custom mapping class
+variable_substitution_map = VariableSubstitutionMap()