diff --git a/README.md b/README.md
index bbe00ba..34ab8ce 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,13 @@ uv run fastapi dev src/allmende_payment_system/app.py
 ```
 A demo user will be created automatically.
 
+### Configuration
+
+A preliminary config system exists and works via environment variables:
+
+    * APS_READ_ONLY: If set, users can make no purchases
+    * APS_PRODUCTION_MODE: If set, demo functionality, like adding money to an account and the demo banner are removed.
+
 ### Testing
 
 APS uses pytest. You can run the test suite with:
diff --git a/src/allmende_payment_system/templates/order.html.jinja b/src/allmende_payment_system/templates/order.html.jinja
index b46cd51..76ed7bb 100644
--- a/src/allmende_payment_system/templates/order.html.jinja
+++ b/src/allmende_payment_system/templates/order.html.jinja
@@ -82,7 +82,8 @@
                     {% elif user.accounts|length == 1 %}
                         <input type="hidden" name="account_id" value="{{ user.accounts[0].id }}">
                     {% endif %}
-                    <button type="submit" class="btn btn-primary">Jetzt Bezahlen</button>
+                    <button type="submit" class="btn btn-primary" {% if read_only_mode %}disabled{% endif %}>Jetzt Bezahlen</button>
+                    {% if read_only_mode %}<span class="text-muted small ms-3">⚠️ Das System befindet sich im schreibgeschützen Modus. Derzeit sind keine Einkäufe möglich.</span>{% endif %}
                 </form>
             </div>
         </div>
diff --git a/src/allmende_payment_system/tools.py b/src/allmende_payment_system/tools.py
index 23e040f..8f0b389 100644
--- a/src/allmende_payment_system/tools.py
+++ b/src/allmende_payment_system/tools.py
@@ -29,6 +29,7 @@ def get_jinja_renderer() -> Jinja2Templates:
     renderer.env.filters["timestamp_de"] = lambda x: x.strftime("%d.%m.%Y %H:%M")
 
     renderer.env.globals["production_mode"] = "APS_PRODUCTION_MODE" in os.environ
+    renderer.env.globals["read_only_mode"] = "APS_READ_ONLY" in os.environ
     return renderer