diff --git a/docs/architecture/adr-payment-boundary.md b/docs/architecture/adr-payment-boundary.md
new file mode 100644
index 0000000..23ef312
--- /dev/null
+++ b/docs/architecture/adr-payment-boundary.md
@@ -0,0 +1,20 @@
+# Architecture Decision Record: Payment Boundary
+
+## Context
+In order to define our payment processing system, we need to establish clear boundaries between different components that handle payments. This includes services responsible for payment requests, notifications, and reconciliation.
+
+## Decision
+We will implement a microservices architecture where each payment-related functionality is managed by a separate service. This allows for better scalability and maintainability. The main services will include:
+- Payment Service: Handles payment transactions.
+- Notification Service: Sends notifications upon payment success or failure.
+- Reconciliation Service: Ensures the integrity of payments across systems.
+
+Additionally, we will enforce communication through a RESTful API approach and use message queues for asynchronous operations between services.
+
+## Alternatives
+1. **Monolithic Architecture**: This was considered but rejected due to scaling limitations.
+2. **Serverless Functions**: While appealing, the complexity of maintaining state and handling different payment types favored a microservices approach.
+
+## Consequences
+Choosing a microservices architecture will introduce operational overhead but it enables us to scale individual components as needed. It accommodates future integrations with third-party payment providers and allows teams to work independently on their respective services without impacting others.
+