diff --git a/src/com/android/services/telephony/rcs/SipTransportController.java b/src/com/android/services/telephony/rcs/SipTransportController.java
index b5950aa..028e49f 100644
--- a/src/com/android/services/telephony/rcs/SipTransportController.java
+++ b/src/com/android/services/telephony/rcs/SipTransportController.java
@@ -19,6 +19,7 @@
 import android.app.role.OnRoleHoldersChangedListener;
 import android.app.role.RoleManager;
 import android.content.Context;
+import android.os.RemoteException;
 import android.os.UserHandle;
 import android.telephony.ims.DelegateRequest;
 import android.telephony.ims.FeatureTagState;
@@ -468,38 +469,64 @@
      * event.
      */
     private void triggerDeregistrationEvent() {
-        if (mPendingUpdateRegistrationFuture != null
-                && !mPendingUpdateRegistrationFuture.isDone()) {
-            // Cancel pending update and replace with a call to deregister now.
-            mPendingUpdateRegistrationFuture.cancel(false);
-            logi("triggerDeregistrationEvent: cancelling existing reg update event: "
-                    + mPendingUpdateRegistrationFuture);
-        }
         logi("triggerDeregistrationEvent: Sending deregister event to ImsService");
-        //TODO hook up registration apis
+        cancelPendingUpdateRegistration();
+
+        IImsRegistration registrationImpl = mRcsManager.getImsRegistration();
+        if (registrationImpl != null) {
+            try {
+                registrationImpl.triggerSipDelegateDeregistration();
+            } catch (RemoteException e) {
+                logi("triggerDeregistrationEvent: received RemoteException: " + e);
+            }
+        }
     }
 
     /**
      * Schedule an update to the IMS registration. If there is an existing update scheduled, cancel
      * it and reschedule.
+     * <p>
+     * We want to wait because this can directly result in changes to the IMS registration on the
+     * network, so we need to wait for a steady state where all changes have been made before
+     * triggering an update to the network registration.
      */
     private void scheduleUpdateRegistration() {
-        if (mPendingUpdateRegistrationFuture != null
-                && !mPendingUpdateRegistrationFuture.isDone()) {
-            // Cancel the old pending operation and reschedule again.
-            mPendingUpdateRegistrationFuture.cancel(false);
-            logi("scheduleUpdateRegistration: cancelling existing reg update event: "
-                    + mPendingUpdateRegistrationFuture);
-        }
+        cancelPendingUpdateRegistration();
+
         ScheduledFuture<?> f = mExecutorService.schedule(this::triggerUpdateRegistrationEvent,
                 mTimerAdapter.getUpdateRegistrationDelayMilliseconds(), TimeUnit.MILLISECONDS);
         logi("scheduleUpdateRegistration: scheduling new event: " + f);
         mPendingUpdateRegistrationFuture = f;
     }
 
+    /**
+     * Cancel an existing pending task to update the IMS registration associated with SIP delegates.
+     */
+    private void cancelPendingUpdateRegistration() {
+        if (mPendingUpdateRegistrationFuture == null
+                || mPendingUpdateRegistrationFuture.isDone()) {
+            return;
+        }
+        // Cancel the old pending operation and reschedule again.
+        mPendingUpdateRegistrationFuture.cancel(false);
+        logi("scheduleUpdateRegistration: cancelling existing reg update event: "
+                + mPendingUpdateRegistrationFuture);
+    }
+
+    /**
+     * Triggers an event to update the IMS registration of the ImsService. Should only be called
+     * from {@link #scheduleUpdateRegistration()}.
+     */
     private void triggerUpdateRegistrationEvent() {
         logi("triggerUpdateRegistrationEvent: Sending update registration event to ImsService");
-        //TODO hook up registration apis
+        IImsRegistration registrationImpl = mRcsManager.getImsRegistration();
+        if (registrationImpl != null) {
+            try {
+                registrationImpl.triggerUpdateSipDelegateRegistration();
+            } catch (RemoteException e) {
+                logi("triggerUpdateRegistrationEvent: received RemoteException: " + e);
+            }
+        }
     }
 
     /**
@@ -607,6 +634,9 @@
      * by another delegate higher in the priority queue.
      */
     private void reevaluateDelegates() {
+        // We need to cancel the pending update now and reschedule IMS registration update for
+        // after the reevaluate is complete.
+        cancelPendingUpdateRegistration();
         if (mEvaluateCompleteFuture != null && !mEvaluateCompleteFuture.isDone()) {
             logw("reevaluateDelegates: last evaluate not done, deferring new request");
             // Defer re-evaluate until after the pending re-evaluate is complete.
@@ -657,10 +687,13 @@
             }, mExecutorService);
         }
 
-        // Executor doesn't matter here, just adding an extra stage to print result.
+        // Executor doesn't matter here, schedule an event to update the IMS registration.
         mEvaluateCompleteFuture = pendingChange
-                .thenAccept((associatedFeatures) -> logi("reevaluateDelegates: reevaluate complete,"
-                        + " feature tags associated: " + associatedFeatures));
+                .thenAccept((associatedFeatures) -> {
+                    logi("reevaluateDelegates: reevaluate complete," + " feature tags associated: "
+                            + associatedFeatures);
+                    scheduleUpdateRegistration();
+                });
         logi("reevaluateDelegates: future created.");
     }
 
@@ -709,13 +742,19 @@
             // CarrierConfigManager
             return;
         }
-        updateRoleCache();
-        // new denied tags will be picked up when reevaluate completes.
-        scheduleThrottledReevaluate();
+        boolean roleChanged = updateRoleCache();
+        if (roleChanged) {
+            triggerDeregistrationEvent();
+            // new denied tags will be picked up when reevaluate completes.
+            scheduleThrottledReevaluate();
+        }
     }
 
 
-    private void updateRoleCache() {
+    /**
+     * @return true, if the role cache has changed, false otherwise.
+     */
+    private boolean updateRoleCache() {
         String newSmsRolePackageName = "";
         try {
             // Only one app can fulfill the SMS role.
@@ -728,9 +767,10 @@
         logi("updateRoleCache: new packageName=" + newSmsRolePackageName);
         if (TextUtils.equals(mCachedSmsRolePackageName, newSmsRolePackageName)) {
             logi("updateRoleCache, skipping, role did not change");
-            return;
+            return false;
         }
         mCachedSmsRolePackageName = newSmsRolePackageName;
+        return true;
     }
 
     /**
diff --git a/tests/src/com/android/TelephonyTestBase.java b/tests/src/com/android/TelephonyTestBase.java
index 502740d..09abb15 100644
--- a/tests/src/com/android/TelephonyTestBase.java
+++ b/tests/src/com/android/TelephonyTestBase.java
@@ -61,9 +61,7 @@
 
     protected final boolean waitForExecutorAction(Executor executor, long timeoutMillis) {
         final CountDownLatch lock = new CountDownLatch(1);
-        Log.i("BRAD", "waitForExecutorAction");
         executor.execute(() -> {
-            Log.i("BRAD", "countdown");
             lock.countDown();
         });
         while (lock.getCount() > 0) {
diff --git a/tests/src/com/android/services/telephony/rcs/SipTransportControllerTest.java b/tests/src/com/android/services/telephony/rcs/SipTransportControllerTest.java
index 89c3ce3..fa27775 100644
--- a/tests/src/com/android/services/telephony/rcs/SipTransportControllerTest.java
+++ b/tests/src/com/android/services/telephony/rcs/SipTransportControllerTest.java
@@ -40,6 +40,7 @@
 import android.telephony.ims.FeatureTagState;
 import android.telephony.ims.ImsException;
 import android.telephony.ims.SipDelegateManager;
+import android.telephony.ims.aidl.IImsRegistration;
 import android.telephony.ims.aidl.ISipDelegate;
 import android.telephony.ims.aidl.ISipDelegateConnectionStateCallback;
 import android.telephony.ims.aidl.ISipDelegateMessageCallback;
@@ -102,6 +103,7 @@
 
     @Mock private RcsFeatureManager mRcsManager;
     @Mock private ISipTransport mSipTransport;
+    @Mock private IImsRegistration mImsRegistration;
     @Mock private ISipDelegateConnectionStateCallback mMockStateCallback;
     @Mock private ISipDelegateMessageCallback mMockMessageCallback;
     @Mock private SipTransportController.SipDelegateControllerFactory
@@ -116,6 +118,7 @@
     public void setUp() throws Exception {
         super.setUp();
         doReturn(mSmsPackageName).when(mMockRoleManager).getRoleHolders(RoleManager.ROLE_SMS);
+        doReturn(mImsRegistration).when(mRcsManager).getImsRegistration();
         mSmsPackageName.add(TEST_PACKAGE_NAME);
         doAnswer(invocation -> {
             Integer subId = invocation.getArgument(0);
@@ -289,6 +292,7 @@
         SipDelegateController c = injectMockDelegateController(TEST_PACKAGE_NAME, r);
         createDelegateAndVerify(controller, c, r, r.getFeatureTags(), Collections.emptySet(),
                 TEST_PACKAGE_NAME);
+        verifyDelegateRegistrationChangedEvent(1 /*times*/, 0 /*waitMs*/);
         triggerFullNetworkRegistrationAndVerify(controller, c);
     }
 
@@ -301,10 +305,11 @@
         SipDelegateController c = injectMockDelegateController(TEST_PACKAGE_NAME, r);
         createDelegateAndVerify(controller, c, r, r.getFeatureTags(), Collections.emptySet(),
                 TEST_PACKAGE_NAME);
+        verifyDelegateRegistrationChangedEvent(1, 0 /*throttle*/);
 
         destroyDelegateAndVerify(controller, c, false,
                 SipDelegateManager.SIP_DELEGATE_DESTROY_REASON_REQUESTED_BY_APP);
-
+        verifyDelegateRegistrationChangedEvent(2 /*times*/, 0 /*waitMs*/);
         triggerFullNetworkRegistrationAndVerifyNever(controller, c);
     }
 
@@ -326,7 +331,8 @@
     @SmallTest
     @Test
     public void createTwoAndDenyOverlappingTags() throws Exception {
-        SipTransportController controller = setupLiveTransportController();
+        SipTransportController controller = setupLiveTransportController(0 /*reeval*/,
+                THROTTLE_MS);
 
         // First delegate requests RCS message + File transfer
         ArraySet<String> firstDelegate = new ArraySet<>(getBaseDelegateRequest().getFeatureTags());
@@ -336,6 +342,8 @@
                 firstDelegateRequest);
         createDelegateAndVerify(controller, c1, firstDelegateRequest, firstDelegate,
                 Collections.emptySet(), TEST_PACKAGE_NAME);
+        // there is a delay in the indication to update reg, so it should not happen yet.
+        verifyNoDelegateRegistrationChangedEvent();
 
         // First delegate requests RCS message + Group RCS message. For this delegate, single RCS
         // message should be denied.
@@ -349,12 +357,14 @@
                 secondDelegateRequest);
         createDelegateAndVerify(controller, c2, secondDelegateRequest, grantedAndDenied.first,
                 grantedAndDenied.second, TEST_PACKAGE_NAME, 1);
+        // a reg changed event should happen after wait.
+        verifyDelegateRegistrationChangedEvent(1, 2 * THROTTLE_MS);
     }
 
     @SmallTest
     @Test
     public void createTwoAndTriggerRoleChange() throws Exception {
-        SipTransportController controller = setupLiveTransportController();
+        SipTransportController controller = setupLiveTransportController(0 /*reeval*/, THROTTLE_MS);
 
         DelegateRequest firstDelegateRequest = getBaseDelegateRequest();
         Set<FeatureTagState> firstDeniedTags = getDeniedTagsForReason(
@@ -364,6 +374,7 @@
                 firstDelegateRequest);
         createDelegateAndVerify(controller, c1, firstDelegateRequest,
                 firstDelegateRequest.getFeatureTags(), Collections.emptySet(), TEST_PACKAGE_NAME);
+        verifyDelegateRegistrationChangedEvent(1 /*times*/, THROTTLE_MS);
 
         DelegateRequest secondDelegateRequest = getBaseDelegateRequest();
         Set<FeatureTagState> secondDeniedTags = getDeniedTagsForReason(
@@ -381,6 +392,10 @@
         CompletableFuture<Boolean> pendingC2Change = setChangeSupportedFeatureTagsFuture(c2,
                 secondDelegateRequest.getFeatureTags(), Collections.emptySet());
         setSmsRoleAndEvaluate(controller, TEST_PACKAGE_NAME_2);
+        // swapping roles should trigger a deregistration event on the ImsService side.
+        verifyDelegateDeregistrationEvent();
+        // there should also not be any new registration changed events
+        verifyDelegateRegistrationChangedEvent(1 /*times*/, THROTTLE_MS);
         // trigger completion stage to run
         waitForExecutorAction(mExecutorService, TIMEOUT_MS);
         verify(c1).changeSupportedFeatureTags(Collections.emptySet(), firstDeniedTags);
@@ -397,12 +412,14 @@
         // ensure we are not blocking executor here
         waitForExecutorAction(mExecutorService, TIMEOUT_MS);
         completePendingChange(pendingC2Change, true);
+        // verify we now get a second registration changed event
+        verifyDelegateRegistrationChangedEvent(2 /*times*/, THROTTLE_MS);
     }
 
     @SmallTest
     @Test
     public void createTwoAndDestroyOlder() throws Exception {
-        SipTransportController controller = setupLiveTransportController();
+        SipTransportController controller = setupLiveTransportController(0 /*reeval*/, THROTTLE_MS);
 
         // First delegate requests RCS message + File transfer
         ArraySet<String> firstDelegate = new ArraySet<>(getBaseDelegateRequest().getFeatureTags());
@@ -412,6 +429,7 @@
                 firstDelegateRequest);
         createDelegateAndVerify(controller, c1, firstDelegateRequest, firstDelegate,
                 Collections.emptySet(), TEST_PACKAGE_NAME);
+        verifyNoDelegateRegistrationChangedEvent();
 
         // First delegate requests RCS message + Group RCS message. For this delegate, single RCS
         // message should be denied.
@@ -425,6 +443,7 @@
                 secondDelegateRequest);
         createDelegateAndVerify(controller, c2, secondDelegateRequest, grantedAndDenied.first,
                 grantedAndDenied.second, TEST_PACKAGE_NAME, 1);
+        verifyNoDelegateRegistrationChangedEvent();
 
         // Destroy the firstDelegate, which should now cause all previously denied tags to be
         // granted to the new delegate.
@@ -436,12 +455,14 @@
         assertTrue(waitForExecutorAction(mExecutorService, TIMEOUT_MS));
         verify(c2).changeSupportedFeatureTags(secondDelegate, Collections.emptySet());
         completePendingChange(pendingC2Change, true);
+
+        verifyDelegateRegistrationChangedEvent(1 /*times*/, THROTTLE_MS);
     }
 
     @SmallTest
     @Test
     public void testThrottling() throws Exception {
-        SipTransportController controller = setupLiveTransportController(THROTTLE_MS);
+        SipTransportController controller = setupLiveTransportController(THROTTLE_MS, THROTTLE_MS);
 
         // First delegate requests RCS message + File transfer
         ArraySet<String> firstDelegate = new ArraySet<>(getBaseDelegateRequest().getFeatureTags());
@@ -480,12 +501,14 @@
                 thirdDelegateRequest, grantedAndDeniedC3.first, grantedAndDeniedC3.second,
                 TEST_PACKAGE_NAME);
 
+        verifyNoDelegateRegistrationChangedEvent();
         assertTrue(scheduleDelayedWait(2 * THROTTLE_MS));
         verifyDelegateChanged(c1, pendingC1Change, firstDelegate, Collections.emptySet(), 0);
         verifyDelegateChanged(c2, pendingC2Change, grantedAndDeniedC2.first,
                 grantedAndDeniedC2.second, 0);
         verifyDelegateChanged(c3, pendingC3Change, grantedAndDeniedC3.first,
                 grantedAndDeniedC3.second, 0);
+        verifyDelegateRegistrationChangedEvent(1, 2 * THROTTLE_MS);
 
         // Destroy the first and second controller in quick succession, this should only generate
         // one reevaluate for the third controller.
@@ -508,6 +531,7 @@
         verify(c3).changeSupportedFeatureTags(thirdDelegate, Collections.emptySet());
         // In total reeval should have only been called twice.
         verify(c3, times(2)).changeSupportedFeatureTags(any(), any());
+        verifyDelegateRegistrationChangedEvent(2 /*times*/, 2 * THROTTLE_MS);
     }
 
     @SmallTest
@@ -521,6 +545,7 @@
                 firstDelegateRequest);
         createDelegateAndVerify(controller, c1, firstDelegateRequest, firstDelegate,
                 Collections.emptySet(), TEST_PACKAGE_NAME);
+        verifyDelegateRegistrationChangedEvent(1 /*times*/, 0 /*waitMs*/);
 
         CompletableFuture<Integer> pendingDestroy =  setDestroyFuture(c1, true,
                 SipDelegateManager.SIP_DELEGATE_DESTROY_REASON_SUBSCRIPTION_TORN_DOWN);
@@ -528,6 +553,7 @@
         waitForExecutorAction(mExecutorService, TIMEOUT_MS);
         verifyDestroyDelegate(controller, c1, pendingDestroy, true /*force*/,
                 SipDelegateManager.SIP_DELEGATE_DESTROY_REASON_SUBSCRIPTION_TORN_DOWN);
+        verifyDelegateRegistrationChangedEvent(2 /*times*/, 0 /*waitMs*/);
     }
 
     @SmallTest
@@ -548,6 +574,7 @@
         waitForExecutorAction(mExecutorService, TIMEOUT_MS);
         verifyDestroyDelegate(controller, c1, pendingDestroy, true /*force*/,
                 SipDelegateManager.SIP_DELEGATE_DESTROY_REASON_SERVICE_DEAD);
+        verifyDelegateRegistrationChangedEvent(1, 0 /*waitMs*/);
     }
 
     @SmallTest
@@ -566,6 +593,7 @@
                 SipDelegateManager.SIP_DELEGATE_DESTROY_REASON_SUBSCRIPTION_TORN_DOWN);
         controller.onDestroy();
         waitForExecutorAction(mExecutorService, TIMEOUT_MS);
+        verifyDelegateDeregistrationEvent();
         // verify change was called.
         verify(c1).destroy(true /*force*/,
                 SipDelegateManager.SIP_DELEGATE_DESTROY_REASON_SUBSCRIPTION_TORN_DOWN);
@@ -578,7 +606,7 @@
     @SmallTest
     @Test
     public void testTimingSubIdChangedAndCreateNewSubId() throws Exception {
-        SipTransportController controller = setupLiveTransportController(THROTTLE_MS);
+        SipTransportController controller = setupLiveTransportController(THROTTLE_MS, 0);
 
         ArraySet<String> firstDelegate = new ArraySet<>(getBaseDelegateRequest().getFeatureTags());
         DelegateRequest firstDelegateRequest = new DelegateRequest(firstDelegate);
@@ -641,13 +669,14 @@
     }
 
     private SipTransportController setupLiveTransportController() throws Exception {
-        return setupLiveTransportController(0 /*throttleMs*/);
+        return setupLiveTransportController(0 /*throttleMs*/, 0 /*regDelayMs*/);
     }
 
-    private SipTransportController setupLiveTransportController(int throttleMs) throws Exception {
+    private SipTransportController setupLiveTransportController(int throttleMs, int regDelayMs)
+            throws Exception {
         mExecutorService = Executors.newSingleThreadScheduledExecutor();
         SipTransportController controller = createControllerAndThrottle(mExecutorService,
-                throttleMs);
+                throttleMs, regDelayMs);
         doReturn(mSipTransport).when(mRcsManager).getSipTransport();
         controller.onAssociatedSubscriptionUpdated(TEST_SUB_ID);
         controller.onRcsConnected(mRcsManager);
@@ -828,12 +857,31 @@
         waitForExecutorAction(mExecutorService, TIMEOUT_MS);
     }
 
+    private void verifyNoDelegateRegistrationChangedEvent() throws Exception {
+        // event is scheduled and then executed.
+        waitForExecutorAction(mExecutorService, TIMEOUT_MS);
+        verify(mImsRegistration, never()).triggerUpdateSipDelegateRegistration();
+    }
+
+    private void verifyDelegateRegistrationChangedEvent(int times, int waitMs)
+            throws Exception {
+        // event is scheduled and then executed.
+        assertTrue(scheduleDelayedWait(waitMs));
+        waitForExecutorAction(mExecutorService, TIMEOUT_MS);
+        verify(mImsRegistration, times(times)).triggerUpdateSipDelegateRegistration();
+    }
+
+
+    private void verifyDelegateDeregistrationEvent() throws Exception {
+        verify(mImsRegistration).triggerSipDelegateDeregistration();
+    }
+
     private SipTransportController createController(ScheduledExecutorService e) {
-        return createControllerAndThrottle(e, 0 /*throttleMs*/);
+        return createControllerAndThrottle(e, 0 /*throttleMs*/, 0 /*regDelayMs*/);
     }
 
     private SipTransportController createControllerAndThrottle(ScheduledExecutorService e,
-            int throttleMs) {
+            int throttleMs, int regDelayMs) {
         return new SipTransportController(mContext, 0 /*slotId*/, TEST_SUB_ID,
                 mMockDelegateControllerFactory, mMockRoleManager,
                 // Remove delays for testing.
@@ -845,7 +893,7 @@
 
                     @Override
                     public int getUpdateRegistrationDelayMilliseconds() {
-                        return 0;
+                        return regDelayMs;
                     }
                 }, e);
     }