diff --git a/append.go b/append.go
index 3e2589b..683b665 100644
--- a/append.go
+++ b/append.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 // Append is a helper function that will append more errors
diff --git a/append_test.go b/append_test.go
index 58ddafa..e5179bf 100644
--- a/append_test.go
+++ b/append_test.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/flatten.go b/flatten.go
index aab8e9a..3fca40f 100644
--- a/flatten.go
+++ b/flatten.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 // Flatten flattens the given error, merging any *Errors together into
diff --git a/flatten_test.go b/flatten_test.go
index e99c410..2d81f12 100644
--- a/flatten_test.go
+++ b/flatten_test.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/format.go b/format.go
index 47f13c4..b06ae9a 100644
--- a/format.go
+++ b/format.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/format_test.go b/format_test.go
index 2b6da1d..77af2da 100644
--- a/format_test.go
+++ b/format_test.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/group.go b/group.go
index 9c29efb..48b68fc 100644
--- a/group.go
+++ b/group.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import "sync"
diff --git a/group_test.go b/group_test.go
index 9d472fd..88795bf 100644
--- a/group_test.go
+++ b/group_test.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/multierror.go b/multierror.go
index f545743..b83d27f 100644
--- a/multierror.go
+++ b/multierror.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/multierror_test.go b/multierror_test.go
index ed1f08c..9fa41a2 100644
--- a/multierror_test.go
+++ b/multierror_test.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/prefix.go b/prefix.go
index 5c477ab..24ef743 100644
--- a/prefix.go
+++ b/prefix.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/prefix_test.go b/prefix_test.go
index 849ec3a..d0eb04a 100644
--- a/prefix_test.go
+++ b/prefix_test.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (
diff --git a/sort.go b/sort.go
index fecb14e..b9f1f49 100644
--- a/sort.go
+++ b/sort.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 // Len implements sort.Interface function for length
diff --git a/sort_test.go b/sort_test.go
index 7fd04e8..b6ff44e 100644
--- a/sort_test.go
+++ b/sort_test.go
@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package multierror
 
 import (