diff --git a/internal/db/migrations/106_add_madrid_office.down.sql b/internal/db/migrations/106_add_madrid_office.down.sql
new file mode 100644
index 0000000..f89e294
--- /dev/null
+++ b/internal/db/migrations/106_add_madrid_office.down.sql
@@ -0,0 +1,28 @@
+-- Revert mig 106 — drop 'madrid' from the office CHECK constraints.
+--
+-- Will fail if any users.office or partner_units.office row carries
+-- 'madrid' — that's intentional (the down has no opinion on the data;
+-- caller must clean up first or accept the failure).
+
+SELECT set_config(
+    'paliad.audit_reason',
+    'mig 106 down: restore pre-madrid office CHECK on users + partner_units',
+    true);
+
+ALTER TABLE paliad.users
+    DROP CONSTRAINT IF EXISTS users_office_check;
+ALTER TABLE paliad.users
+    ADD CONSTRAINT users_office_check
+    CHECK (office IN (
+        'munich', 'duesseldorf', 'hamburg',
+        'amsterdam', 'london', 'paris', 'milan'
+    ));
+
+ALTER TABLE paliad.partner_units
+    DROP CONSTRAINT IF EXISTS partner_units_office_check;
+ALTER TABLE paliad.partner_units
+    ADD CONSTRAINT partner_units_office_check
+    CHECK (office IN (
+        'munich', 'duesseldorf', 'hamburg',
+        'amsterdam', 'london', 'paris', 'milan'
+    ));
diff --git a/internal/db/migrations/106_add_madrid_office.up.sql b/internal/db/migrations/106_add_madrid_office.up.sql
new file mode 100644
index 0000000..a2c1f62
--- /dev/null
+++ b/internal/db/migrations/106_add_madrid_office.up.sql
@@ -0,0 +1,42 @@
+-- mig 106 — add 'madrid' to firm office CHECK constraints
+--
+-- m's ask 2026-05-20 09:42: add Madrid as an HLC office, alongside the
+-- existing seven (munich, duesseldorf, hamburg, amsterdam, london,
+-- paris, milan). Two active CHECK constraints to extend:
+--   - paliad.users.office          (mig 002)
+--   - paliad.partner_units.office  (mig 018; renamed mig 024 + mig 027)
+--
+-- The Go-side source of truth lives in internal/offices/offices.go;
+-- this migration keeps the DB in sync.
+--
+-- Long-term, the admin area will let firms manage their own office
+-- list (separate issue) — but for now the list is hard-coded here
+-- + offices.go.
+--
+-- Non-blocking: extending a CHECK constraint is a metadata-only change
+-- on a small enum-style column.
+
+SELECT set_config(
+    'paliad.audit_reason',
+    'mig 106: add madrid to firm office CHECK on users + partner_units',
+    true);
+
+ALTER TABLE paliad.users
+    DROP CONSTRAINT IF EXISTS users_office_check;
+ALTER TABLE paliad.users
+    ADD CONSTRAINT users_office_check
+    CHECK (office IN (
+        'munich', 'duesseldorf', 'hamburg',
+        'amsterdam', 'london', 'paris', 'milan',
+        'madrid'
+    ));
+
+ALTER TABLE paliad.partner_units
+    DROP CONSTRAINT IF EXISTS partner_units_office_check;
+ALTER TABLE paliad.partner_units
+    ADD CONSTRAINT partner_units_office_check
+    CHECK (office IN (
+        'munich', 'duesseldorf', 'hamburg',
+        'amsterdam', 'london', 'paris', 'milan',
+        'madrid'
+    ));
diff --git a/internal/offices/offices.go b/internal/offices/offices.go
index 03e3e0e..561cc73 100644
--- a/internal/offices/offices.go
+++ b/internal/offices/offices.go
@@ -1,7 +1,8 @@
 // Package offices is the single source of truth for the firm's office list.
 //
-// The keys here must stay in sync with the CHECK constraint on
-// paliad.users.office and paliad.akten.owning_office (migration 001).
+// The keys here must stay in sync with the CHECK constraints on
+// paliad.users.office (mig 002) and paliad.partner_units.office
+// (mig 018, renamed mig 024 + mig 027). Madrid added mig 106.
 package offices
 
 // Office is a single firm office with its i18n-ready labels.
@@ -20,6 +21,7 @@ var All = []Office{
 	{Key: "london", LabelDE: "London", LabelEN: "London"},
 	{Key: "paris", LabelDE: "Paris", LabelEN: "Paris"},
 	{Key: "milan", LabelDE: "Mailand", LabelEN: "Milan"},
+	{Key: "madrid", LabelDE: "Madrid", LabelEN: "Madrid"},
 }
 
 // IsValid reports whether the given key names a known office.
diff --git a/internal/offices/offices_test.go b/internal/offices/offices_test.go
index 0af07bb..52c73d8 100644
--- a/internal/offices/offices_test.go
+++ b/internal/offices/offices_test.go
@@ -3,7 +3,7 @@ package offices
 import "testing"
 
 func TestIsValid(t *testing.T) {
-	for _, key := range []string{"munich", "duesseldorf", "hamburg", "amsterdam", "london", "paris", "milan"} {
+	for _, key := range []string{"munich", "duesseldorf", "hamburg", "amsterdam", "london", "paris", "milan", "madrid"} {
 		if !IsValid(key) {
 			t.Errorf("IsValid(%q) = false, want true", key)
 		}