diff --git a/docs/diagrams/case-found-sign-up-for-reminder-reminder-already-set.puml b/docs/diagrams/case-found-sign-up-for-reminder-reminder-already-set.puml
new file mode 100755
index 0000000..d4698f5
--- /dev/null
+++ b/docs/diagrams/case-found-sign-up-for-reminder-reminder-already-set.puml
@@ -0,0 +1,8 @@
+@startuml
+skinparam sequenceMessageAlign center
+
+User -> Server: 01-AB-23456
+Server -> User: We found case "01-AB-23456" on 7/28/2022 1:00 PM @ Family/Criminal Courtroom 2A Chittenden, VT.\nReply with YES if you would like a courtesy reminder the day before or reply with NO to start over.
+User -> Server: Yes
+Server -> User: A reminder to notify you on case "01-AB-23456" taking place on 7/28/2022 1:00 PM @ Family/Criminal\n Courtroom 2A Chittenden, VT has already been set.
+@enduml
\ No newline at end of file
diff --git a/pages/api/sms/[instance]/index.ts b/pages/api/sms/[instance]/index.ts
index 7e0afb9..aee0d85 100644
--- a/pages/api/sms/[instance]/index.ts
+++ b/pages/api/sms/[instance]/index.ts
@@ -135,23 +135,50 @@ const handleText = async (req:NextApiRequest, res:NextApiResponse, input:string,
           // let's check for a yes
           if (response.toLowerCase() === 'yes') {
             let c = cases[0];
-            await ReminderDao.create({
+
+            // check if a reminder is already active
+            const reminders = await ReminderDao.find({
+              active: true,
               uid: c.uid,
               number: c.number,
               phone,
-            });
+            }).exec();
 
-            logger.info(`${phone} (${instance})[${state}]: reminder set`, { metadata: {
-              service: `/api/sms/${instance}`,
-              cookies,
-              instance,
-              input,
-              phone,
-              case: c,
-              state,
-              result: 'reminder set',
-            }});
-            res.send(smsResponse.reminderYes(c).toString());
+            if (reminders.length === 0) {
+              // create a new reminder document
+              // if no 'active' reminder documents are found
+              // matching the case uid, docket number, and phone number
+              await ReminderDao.create({
+                uid: c.uid,
+                number: c.number,
+                phone,
+              });
+              logger.info(`${phone} (${instance})[${state}]: reminder set`, { metadata: {
+                service: `/api/sms/${instance}`,
+                cookies,
+                instance,
+                input,
+                phone,
+                case: c,
+                state,
+                result: 'reminder set',
+              }});
+              res.send(smsResponse.reminderYes(c).toString());
+            } else {
+              // at least one reminder document in the collection already exists
+              // for the phone number `phone` to be reminded about case docket `c.number`
+              logger.info(`${phone} (${instance})[${state}]: reminder already set`, { metadata: {
+                service: `/api/sms/${instance}`,
+                cookies,
+                instance,
+                input,
+                phone,
+                case: c,
+                state,
+                result: 'reminder already set',
+              }});
+              res.send(smsResponse.reminderActive(c).toString());
+            }
           }
           // send help due to unexpected response
           else {
@@ -179,23 +206,49 @@ const handleText = async (req:NextApiRequest, res:NextApiResponse, input:string,
           // if a number was given lets check to see if it maps to a case index
           if (response === parseInt(response).toString() && index >= 0 && index < cases.length) {
             let c = cases[index];
-            await ReminderDao.create({
+            // check if a reminder is already active
+            const reminders = await ReminderDao.find({
+              active: true,
               uid: c.uid,
               number: c.number,
               phone,
-            });
+            }).exec();
 
-            logger.info(`${phone} (${instance})[${state}]: reminder set`, { metadata: {
-              service: `/api/sms/${instance}`,
-              cookies,
-              instance,
-              input,
-              phone,
-              case: c,
-              state,
-              result: 'reminder set',
-            }});
-            res.send(smsResponse.reminderYes(c).toString());
+            if (reminders.length === 0) {
+              // create a new reminder document
+              // if no 'active' reminder documents are found
+              // matching the case uid, docket number, and phone number
+              await ReminderDao.create({
+                uid: c.uid,
+                number: c.number,
+                phone,
+              });
+              logger.info(`${phone} (${instance})[${state}]: reminder set`, { metadata: {
+                service: `/api/sms/${instance}`,
+                cookies,
+                instance,
+                input,
+                phone,
+                case: c,
+                state,
+                result: 'reminder set',
+              }});
+              res.send(smsResponse.reminderYes(c).toString());
+            } else {
+              // at least one reminder document in the collection already exists
+              // for the phone number `phone` to be reminded about case docket `c.number`
+              logger.info(`${phone} (${instance})[${state}]: reminder already set`, { metadata: {
+                service: `/api/sms/${instance}`,
+                cookies,
+                instance,
+                input,
+                phone,
+                case: c,
+                state,
+                result: 'reminder already set',
+              }});
+              res.send(smsResponse.reminderActive(c).toString());
+            }
           }
           // send help due to unexpected response
           else {
diff --git a/utils/sms-response.ts b/utils/sms-response.ts
index db58fdb..7c864cc 100644
--- a/utils/sms-response.ts
+++ b/utils/sms-response.ts
@@ -53,11 +53,18 @@ const reminderNo = (website:string) => {
   return resp;
 };
 
+const reminderActive = (c:Case) => {
+  var resp = new MessagingResponse();
+  resp.message(`A reminder to notify you on case "${c.number}" taking place on ${moment(c.date).tz(timezone).format('l LT')} @ ${c.address} has already been set.`);
+  return resp;
+}
+
 export default {
   caseNotFound,
   caseFound,
   error,
   help,
+  reminderActive,
   reminderNo,
   reminderYes,
 };
\ No newline at end of file