diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..f39e076
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Buttercode Systems
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
index 9c0e72c..38ff1e0 100644
--- a/README.md
+++ b/README.md
@@ -59,3 +59,13 @@ The complete application is now present in [buttercode101/InvoiceFlow](https://g
 - [Contributing](CONTRIBUTING.md) · [Security reporting](SECURITY.md)
 
 Current source version: **0.4.0**. Tax fields are aids, not SARS verification or tax advice.
+
+## Source layout note
+
+`dist/` is the deployable source tree, not generated build output: there is
+no bundler or build step. `dist/core.js` (domain logic, imported directly by
+`tests/`), `dist/app.js` (UI) and `dist/pdf.js` are hand-maintained ES
+modules served as-is by any static host and copied verbatim into the Android
+assets by `android/prepare.mjs`. `src/lib/validation.js` is the only file
+outside `dist/` (used by the vitest UI tests). If you add a build step later,
+update `tests/` imports, `sw.js` precache and `android/prepare.mjs` together.