diff --git a/components/adminComponents/AdminHeader.tsx b/components/adminComponents/AdminHeader.tsx
index bd5b16c9..2b8ebabe 100644
--- a/components/adminComponents/AdminHeader.tsx
+++ b/components/adminComponents/AdminHeader.tsx
@@ -67,6 +67,14 @@ export default function AdminHeader() {
               Stats at a Glance
             </NavLink>
           )}
+          <NavLink
+            href="/admin/waitlist"
+            exact={true}
+            activeOptions={'border-b-4 border-primaryDark text-complementaryDark'}
+            className="mx-4 py-2"
+          >
+            Waitlist Check-in
+          </NavLink>
         </div>
       </header>
       <div className="mt-4 md:hidden ">
diff --git a/lib/types.d.ts b/lib/types.d.ts
index f83d3e5f..41fb8b42 100644
--- a/lib/types.d.ts
+++ b/lib/types.d.ts
@@ -108,6 +108,7 @@ type Registration = {
   website?: string;
   resume?: string;
   companies: Companies[];
+  waitlistNumber?: number;
   //claims: []; //Array of Strings will be used to id any claims (lunch, merch, etc.) made by user
 };
 
diff --git a/pages/admin/scan/index.tsx b/pages/admin/scan/index.tsx
index db5d44be..6cf1cad7 100644
--- a/pages/admin/scan/index.tsx
+++ b/pages/admin/scan/index.tsx
@@ -17,6 +17,7 @@ const successStrings = {
   unexpectedError: 'Unexpected error...',
   notCheckedIn: "User hasn't checked in!",
   invalidFormat: 'Invalid hacker tag format...',
+  lateCheckInIneligible: 'User is not eligible for late check-in...',
 };
 
 interface UserProfile extends Omit<Registration, 'user'> {
@@ -109,6 +110,8 @@ export default function Admin() {
           return setSuccess(successStrings.alreadyClaimed);
         } else if (result.status === 403) {
           return setSuccess(successStrings.notCheckedIn);
+        } else if (result.status === 400) {
+          return setSuccess(successStrings.lateCheckInIneligible);
         } else if (result.status !== 200) {
           return setSuccess(successStrings.unexpectedError);
         }
diff --git a/pages/admin/waitlist/index.tsx b/pages/admin/waitlist/index.tsx
new file mode 100644
index 00000000..14982b3b
--- /dev/null
+++ b/pages/admin/waitlist/index.tsx
@@ -0,0 +1,143 @@
+import Head from 'next/head';
+import AdminHeader from '../../../components/adminComponents/AdminHeader';
+import { useState } from 'react';
+import QRCodeReader from '../../../components/dashboardComponents/QRCodeReader';
+import { RequestHelper } from '../../../lib/request-helper';
+import { useAuthContext } from '../../../lib/user/AuthContext';
+import { isAuthorized } from '..';
+
+const SCAN_STATUS = {
+  successful: 'Check-in successful...',
+  invalidUser: 'Invalid user...',
+  unexpectedError: 'Unexpected error...',
+  invalidFormat: 'Invalid hacker tag format...',
+};
+
+type ApiResponseType = {
+  statusCode: number;
+  msg: string;
+};
+
+type ApiRequestType = {
+  userId: string;
+};
+
+export default function WaitlistCheckinPage() {
+  const [scanStatus, setScanStatus] = useState<ApiResponseType | undefined>(undefined);
+  const { user, isSignedIn } = useAuthContext();
+  const [upperBoundValue, setUpperBoundValue] = useState<number>(0);
+
+  const handleUpdateLateCheckInUpperBound = async (value: number) => {
+    try {
+      const { data } = await RequestHelper.post<{ value: number }, ApiResponseType>(
+        '/api/waitlist/upperbound',
+        {
+          headers: {
+            Authorization: user.token,
+            'Content-Type': 'application/json',
+          },
+        },
+        {
+          value,
+        },
+      );
+      if (data.statusCode !== 200) {
+        alert('Unexpected error...');
+        console.error(data.msg);
+      } else {
+        alert(data.msg);
+      }
+    } catch (error) {
+      alert('Unexpected error...');
+      console.error(error);
+    }
+  };
+
+  const handleScan = async (data: string) => {
+    if (!data.startsWith('hack:')) {
+      setScanStatus({
+        statusCode: 400,
+        msg: SCAN_STATUS.invalidFormat,
+      });
+    }
+    try {
+      const { data: resData } = await RequestHelper.post<ApiRequestType, ApiResponseType>(
+        '/api/waitlist',
+        {
+          headers: {
+            Authorization: user.token,
+            'Content-Type': 'application/json',
+          },
+        },
+        {
+          userId: data.replaceAll('hack:', ''),
+        },
+      );
+      setScanStatus(resData);
+    } catch (error) {
+      setScanStatus({
+        statusCode: 500,
+        msg: SCAN_STATUS.unexpectedError,
+      });
+      console.error(error);
+    }
+  };
+
+  if (!isSignedIn || !isAuthorized(user))
+    return <div className="text-2xl font-black text-center">Unauthorized</div>;
+
+  return (
+    <div className="flex flex-col flex-grow">
+      <Head>
+        <title>HackPortal - Admin</title>
+        <meta name="description" content="HackPortal's Admin Page" />
+      </Head>
+      <section className="p-4">
+        <AdminHeader />
+      </section>
+      <div className="flex flex-col justify-center">
+        <div className="my-6 mx-auto">
+          <div className="flex gap-x-4 mb-10 items-center">
+            <h1 className="text-lg">Set late check-in eligible upper bound: </h1>
+            <input
+              type="number"
+              name="lateCheckInUpperBound"
+              onChange={(e) => setUpperBoundValue(parseInt(e.target.value))}
+            />
+            <button
+              className="rounded-lg border border-green-900 p-3 text-green-900 hover:bg-green-400"
+              onClick={async () => {
+                await handleUpdateLateCheckInUpperBound(upperBoundValue);
+              }}
+            >
+              Update
+            </button>
+          </div>
+          <div className="flex flex-col gap-y-4">
+            {scanStatus === undefined ? (
+              <QRCodeReader width={200} height={200} callback={handleScan} />
+            ) : (
+              <>
+                <div
+                  className={`text-center text-3xl ${
+                    scanStatus.statusCode < 400 ? 'font-black' : 'text-red-600'
+                  }`}
+                >
+                  {scanStatus.msg}
+                </div>
+                <div className="flex gap-x-5 mx-auto">
+                  <div
+                    onClick={() => setScanStatus(undefined)}
+                    className="w-min-5 m-3 rounded-lg text-center text-lg font-black p-3 cursor-pointer hover:bg-green-300 border border-green-800 text-green-900"
+                  >
+                    Next Scan
+                  </div>
+                </div>
+              </>
+            )}
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+}
diff --git a/pages/api/scan.tsx b/pages/api/scan.tsx
index 7bafd54c..39e0e56b 100644
--- a/pages/api/scan.tsx
+++ b/pages/api/scan.tsx
@@ -13,6 +13,8 @@ const SCANTYPES_COLLECTION = '/scan-types';
 // Used to dictate that user attempted to claim swag without checking in
 const ILLEGAL_SCAN_NAME = 'Illegal Scan';
 
+// Set this to false if application accept/reject feature is not needed.
+const ENABLE_ACCEPT_REJECT_FEATURE = true;
 /**
  *
  * Check if a user has checked in into the event
@@ -32,6 +34,27 @@ async function userAlreadyCheckedIn(scans: string[]) {
   return ok;
 }
 
+async function checkLateCheckInEligible(userData: Registration) {
+  const lateCheckInManager = await db.collection('/miscellaneous').doc('lateCheckInManager').get();
+  if (lateCheckInManager && lateCheckInManager.exists) {
+    return (
+      userData.waitlistNumber !== undefined &&
+      userData.waitlistNumber <= lateCheckInManager.data().allowedCheckInUpperBound
+    );
+  }
+  // if no late check-in doc, assume that organizers does not want to use this feature.
+  return true;
+}
+
+async function checkUserIsRejected(userId: string): Promise<boolean> {
+  const snapshot = await db.collection('acceptreject').where('hackerId', '==', userId).get();
+  if (snapshot.docs.length === 0) {
+    return true;
+  }
+  // if user is not accepted by the time they are being checked in, assume that they will be rejected
+  return snapshot.docs[0].data().status !== 'Accepted';
+}
+
 /**
  *
  * Check if provided scan name corresponds to a check in scan-type
@@ -91,6 +114,17 @@ async function handleScan(req: NextApiRequest, res: NextApiResponse) {
     const userCheckedIn = await userAlreadyCheckedIn(scans);
     const scanIsCheckInEvent = await checkIfScanIsCheckIn(bodyData.scan);
 
+    if (!userCheckedIn && scanIsCheckInEvent && ENABLE_ACCEPT_REJECT_FEATURE) {
+      // if user is reject and not eligible for late check-in yet, throw error
+      const userIsRejected = await checkUserIsRejected(snapshot.id);
+      const lateCheckInEligible = await checkLateCheckInEligible(snapshot.data() as Registration);
+      if (userIsRejected && !lateCheckInEligible) {
+        return res
+          .status(400)
+          .json({ code: 'non eligible', message: 'User is not eligible for late check-in yet...' });
+      }
+    }
+
     if (!userCheckedIn && !scanIsCheckInEvent) {
       scans.push({
         name: ILLEGAL_SCAN_NAME,
diff --git a/pages/api/waitlist/index.ts b/pages/api/waitlist/index.ts
new file mode 100644
index 00000000..f7f47512
--- /dev/null
+++ b/pages/api/waitlist/index.ts
@@ -0,0 +1,117 @@
+import { NextApiRequest, NextApiResponse } from 'next';
+import { userIsAuthorized } from '../../../lib/authorization/check-authorization';
+import initializeApi from '../../../lib/admin/init';
+import { firestore } from 'firebase-admin';
+
+initializeApi();
+const db = firestore();
+const MAX_ASSIGN_ATTEMPT = 10;
+
+type FirebaseDocumentRefType = FirebaseFirestore.DocumentReference<FirebaseFirestore.DocumentData>;
+
+async function getUserDocRef(
+  userId: string,
+): Promise<{ userDocRef: FirebaseDocumentRefType; userData: any } | null> {
+  const snapshot = await db.collection('/registrations').doc(userId).get();
+  if (snapshot && snapshot.exists) {
+    return {
+      userDocRef: snapshot.ref,
+      userData: snapshot.data(),
+    };
+  }
+  return null;
+}
+
+async function assignNewCheckInNumberToUser(userDocRef: FirebaseDocumentRefType): Promise<number> {
+  const snapshot = await db.collection('/miscellaneous').doc('lateCheckInManager').get();
+  if (snapshot && snapshot.exists) {
+    const { nextAvailableNumber } = snapshot.data();
+
+    // Attempt to assign id to user constant number of times. If unsuccessful, throw error and ask user to try again.
+    let assignSuccessful = false;
+    for (let iter = 0; iter < MAX_ASSIGN_ATTEMPT; iter++) {
+      try {
+        await userDocRef.update({
+          waitlistNumber: nextAvailableNumber,
+        });
+        assignSuccessful = true;
+        break;
+      } catch (error) {
+        console.error(error);
+        continue;
+      }
+    }
+    if (!assignSuccessful) {
+      throw new Error('Unsuccessfully assigned check-in number to user...');
+    }
+    await snapshot.ref.update({
+      nextAvailableNumber: nextAvailableNumber + 1,
+    });
+    return nextAvailableNumber;
+  } else {
+    // First assignable number will be 1.
+    await snapshot.ref.set(
+      {
+        nextAvailableNumber: 1,
+        allowedCheckInUpperBound: 0,
+      },
+      { merge: true },
+    );
+    return 1;
+  }
+}
+
+function alreadyHasCheckInNumber(userData: any) {
+  return Object.hasOwn(userData, 'waitlistNumber');
+}
+
+async function handlePostRequest(req: NextApiRequest, res: NextApiResponse) {
+  const { headers } = req;
+  const userToken = headers['authorization'];
+  const isAuthorized = await userIsAuthorized(userToken, ['admin', 'super_admin']);
+  if (!isAuthorized) {
+    return res.status(403).json({
+      statusCode: 403,
+      msg: 'Request is not authorized to perform admin functionality',
+    });
+  }
+  try {
+    const fetchUserDocRefResult = await getUserDocRef(req.body.userId);
+    if (!fetchUserDocRefResult) {
+      return res.status(400).json({
+        statusCode: 400,
+        msg: 'User not found...',
+      });
+    }
+    const { userDocRef, userData } = fetchUserDocRefResult;
+    if (alreadyHasCheckInNumber(userData)) {
+      return res.status(400).json({
+        statusCode: 400,
+        msg: 'User already had check-in number...',
+      });
+    }
+    const checkInNumber = await assignNewCheckInNumberToUser(userDocRef);
+    return res.status(200).json({
+      statusCode: 200,
+      msg: `User's check in number is ${checkInNumber}`,
+    });
+  } catch (error) {
+    console.error(error);
+    return res.status(500).json({
+      statusCode: 500,
+      msg: 'Unexpected error...',
+    });
+  }
+}
+
+export default function handler(req: NextApiRequest, res: NextApiResponse) {
+  const { method } = req;
+  switch (method) {
+    case 'POST': {
+      return handlePostRequest(req, res);
+    }
+    default: {
+      return res.status(404).json({ msg: 'Route not found' });
+    }
+  }
+}
diff --git a/pages/api/waitlist/upperbound.ts b/pages/api/waitlist/upperbound.ts
new file mode 100644
index 00000000..2b884263
--- /dev/null
+++ b/pages/api/waitlist/upperbound.ts
@@ -0,0 +1,55 @@
+import { NextApiRequest, NextApiResponse } from 'next';
+import { userIsAuthorized } from '../../../lib/authorization/check-authorization';
+import initializeApi from '../../../lib/admin/init';
+import { firestore } from 'firebase-admin';
+
+initializeApi();
+const db = firestore();
+
+async function handlePostRequest(req: NextApiRequest, res: NextApiResponse) {
+  const { headers } = req;
+  const userToken = headers['authorization'];
+  const isAuthorized = await userIsAuthorized(userToken, ['admin', 'super_admin']);
+  if (!isAuthorized) {
+    return res.status(403).json({
+      statusCode: 403,
+      msg: 'Request is not authorized to perform admin functionality',
+    });
+  }
+  try {
+    const snapshot = await db.collection('/miscellaneous').doc('lateCheckInManager').get();
+    if (snapshot && snapshot.exists) {
+      await snapshot.ref.update({
+        allowedCheckInUpperBound: req.body.value,
+      });
+    } else {
+      await snapshot.ref.set({
+        allowedCheckInUpperBound: req.body.value,
+        version: 1,
+        nextAvailableNumber: 1,
+      });
+    }
+    return res.status(200).json({
+      statusCode: 200,
+      msg: 'Sucessful',
+    });
+  } catch (error) {
+    console.error(error);
+    return res.status(500).json({
+      statusCode: 500,
+      msg: 'Unexpected error...',
+    });
+  }
+}
+
+export default function handler(req: NextApiRequest, res: NextApiResponse) {
+  const { method } = req;
+  switch (method) {
+    case 'POST': {
+      return handlePostRequest(req, res);
+    }
+    default: {
+      return res.status(404).json({ msg: 'Route not found' });
+    }
+  }
+}