diff --git a/index.html b/index.html
index 294ecdca..f2323dd3 100644
--- a/index.html
+++ b/index.html
@@ -490,6 +490,12 @@ <h3>Proofs</h3>
 [[XMLSCHEMA11-2]] combined date and time string.
           </dd>
 
+          <dt>expires</dt>
+          <dd>
+An OPTIONAL property that conveys the date and time that a proof expires and that, if present, MUST be
+specified as an [[XMLSCHEMA11-2]] combined date and time string.
+          </dd>
+
           <dt>domain</dt>
           <dd>
 The creator of a proof SHOULD include a string value that indicates its intended usage, which a verifier SHOULD use to ensure the proof was intended to be used by them. The