diff --git a/java/google/registry/model/eppcommon/Address.java b/java/google/registry/model/eppcommon/Address.java
index 98157382c..c7b3ef6ad 100644
--- a/java/google/registry/model/eppcommon/Address.java
+++ b/java/google/registry/model/eppcommon/Address.java
@@ -94,9 +94,21 @@ public class Address extends ImmutableObject implements Jsonifiable {
         .build();
   }
 
+  @VisibleForTesting
+  public Builder<? extends Address> asBuilder() {
+    return new Builder<>(clone(this));
+  }
+
   /** A builder for constructing {@link Address}. */
   @VisibleForTesting
   public static class Builder<T extends Address> extends Buildable.Builder<T> {
+
+    public Builder() {}
+
+    protected Builder(T instance) {
+      super(instance);
+    }
+
     public Builder<T> setStreet(ImmutableList<String> street) {
       checkArgument(
           street == null || (!street.isEmpty() && street.size() <= 3),
diff --git a/java/google/registry/model/registrar/RegistrarAddress.java b/java/google/registry/model/registrar/RegistrarAddress.java
index d9fd237ef..239a23a83 100644
--- a/java/google/registry/model/registrar/RegistrarAddress.java
+++ b/java/google/registry/model/registrar/RegistrarAddress.java
@@ -17,6 +17,7 @@ package google.registry.model.registrar;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static google.registry.util.CollectionUtils.forceEmptyToNull;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.googlecode.objectify.annotation.Embed;
 import google.registry.model.eppcommon.Address;
 
@@ -30,8 +31,20 @@ import google.registry.model.eppcommon.Address;
 @Embed
 public class RegistrarAddress extends Address {
 
+  @Override
+  @VisibleForTesting
+  public Builder asBuilder() {
+    return new Builder(clone(this));
+  }
+
   /** Builder for {@link RegistrarAddress}. */
   public static class Builder extends Address.Builder<RegistrarAddress> {
+    public Builder() {}
+
+    private Builder(RegistrarAddress instance) {
+      super(instance);
+    }
+
     @Override
     public RegistrarAddress build() {
       RegistrarAddress instance = getInstance();
diff --git a/javatests/google/registry/ui/server/registrar/RegistrarSettingsActionTest.java b/javatests/google/registry/ui/server/registrar/RegistrarSettingsActionTest.java
index 4fce2b8b6..3930b720e 100644
--- a/javatests/google/registry/ui/server/registrar/RegistrarSettingsActionTest.java
+++ b/javatests/google/registry/ui/server/registrar/RegistrarSettingsActionTest.java
@@ -28,12 +28,18 @@ import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import google.registry.export.sheet.SyncRegistrarsSheetAction;
+import google.registry.model.registrar.Registrar;
 import google.registry.request.HttpException.ForbiddenException;
 import google.registry.request.auth.AuthResult;
+import google.registry.testing.CertificateSamples;
 import google.registry.testing.TaskQueueHelper.TaskMatcher;
+import google.registry.util.CidrAddressBlock;
 import java.util.Map;
+import java.util.function.BiFunction;
+import java.util.function.Function;
 import javax.mail.internet.InternetAddress;
 import javax.servlet.http.HttpServletRequest;
 import org.json.simple.JSONValue;
@@ -158,6 +164,125 @@ public class RegistrarSettingsActionTest extends RegistrarSettingsActionTestCase
     assertNoTasksEnqueued("sheet");
   }
 
+  private <T> void doTestUpdate(
+      Function<Registrar, T> getter,
+      T newValue,
+      BiFunction<Registrar.Builder, T, Registrar.Builder> setter) {
+    Registrar registrar = loadRegistrar(CLIENT_ID);
+    assertThat(getter.apply(registrar)).isNotEqualTo(newValue);
+
+    Map<String, Object> response =
+        action.handleJsonRequest(
+            ImmutableMap.of(
+                "op", "update",
+                "args", setter.apply(registrar.asBuilder(), newValue).build().toJsonMap()));
+
+    registrar = loadRegistrar(CLIENT_ID);
+    assertThat(response).containsEntry("status", "SUCCESS");
+    assertThat(response).containsEntry("results", asList(registrar.toJsonMap()));
+    assertThat(getter.apply(registrar)).isEqualTo(newValue);
+  }
+
+  @Test
+  public void testUpdate_premiumPriceAck() throws Exception {
+    doTestUpdate(
+        Registrar::getPremiumPriceAckRequired, true, Registrar.Builder::setPremiumPriceAckRequired);
+  }
+
+  @Test
+  public void testUpdate_whoisServer() throws Exception {
+    doTestUpdate(Registrar::getWhoisServer, "new-whois.example", Registrar.Builder::setWhoisServer);
+  }
+
+  @Test
+  public void testUpdate_referralUrl() throws Exception {
+    doTestUpdate(
+        Registrar::getReferralUrl, "new-reference-url.example", Registrar.Builder::setReferralUrl);
+  }
+
+  @Test
+  public void testUpdate_phoneNumber() throws Exception {
+    doTestUpdate(Registrar::getPhoneNumber, "+1.2345678900", Registrar.Builder::setPhoneNumber);
+  }
+
+  @Test
+  public void testUpdate_faxNumber() throws Exception {
+    doTestUpdate(Registrar::getFaxNumber, "+1.2345678900", Registrar.Builder::setFaxNumber);
+  }
+
+  @Test
+  public void testUpdate_url() throws Exception {
+    doTestUpdate(Registrar::getUrl, "new-url.example", Registrar.Builder::setUrl);
+  }
+
+  @Test
+  public void testUpdate_ipAddressWhitelist() throws Exception {
+    doTestUpdate(
+        Registrar::getIpAddressWhitelist,
+        ImmutableList.of(CidrAddressBlock.create("1.1.1.0/24")),
+        Registrar.Builder::setIpAddressWhitelist);
+  }
+
+  @Test
+  public void testUpdate_clientCertificate() throws Exception {
+    doTestUpdate(
+        Registrar::getClientCertificate,
+        CertificateSamples.SAMPLE_CERT,
+        (builder, s) -> builder.setClientCertificate(s, clock.nowUtc()));
+  }
+
+  @Test
+  public void testUpdate_failoverClientCertificate() throws Exception {
+    doTestUpdate(
+        Registrar::getFailoverClientCertificate,
+        CertificateSamples.SAMPLE_CERT,
+        (builder, s) -> builder.setFailoverClientCertificate(s, clock.nowUtc()));
+  }
+
+  @Test
+  public void testUpdate_localizedAddress_city() throws Exception {
+    doTestUpdate(
+        Registrar::getLocalizedAddress,
+        loadRegistrar(CLIENT_ID).getLocalizedAddress().asBuilder().setCity("newCity").build(),
+        Registrar.Builder::setLocalizedAddress);
+  }
+
+  @Test
+  public void testUpdate_localizedAddress_countryCode() throws Exception {
+    doTestUpdate(
+        Registrar::getLocalizedAddress,
+        loadRegistrar(CLIENT_ID).getLocalizedAddress().asBuilder().setCountryCode("GB").build(),
+        Registrar.Builder::setLocalizedAddress);
+  }
+
+  @Test
+  public void testUpdate_localizedAddress_state() throws Exception {
+    doTestUpdate(
+        Registrar::getLocalizedAddress,
+        loadRegistrar(CLIENT_ID).getLocalizedAddress().asBuilder().setState("NJ").build(),
+        Registrar.Builder::setLocalizedAddress);
+  }
+
+  @Test
+  public void testUpdate_localizedAddress_street() throws Exception {
+    doTestUpdate(
+        Registrar::getLocalizedAddress,
+        loadRegistrar(CLIENT_ID)
+            .getLocalizedAddress()
+            .asBuilder()
+            .setStreet(ImmutableList.of("new street"))
+            .build(),
+        Registrar.Builder::setLocalizedAddress);
+  }
+
+  @Test
+  public void testUpdate_localizedAddress_zip() throws Exception {
+    doTestUpdate(
+        Registrar::getLocalizedAddress,
+        loadRegistrar(CLIENT_ID).getLocalizedAddress().asBuilder().setZip("new zip").build(),
+        Registrar.Builder::setLocalizedAddress);
+  }
+
   private static String getLastUpdateTime() {
     return loadRegistrar(CLIENT_ID).getLastUpdateTime().toString();
   }