diff --git a/make_post_sell/static/js/auction.js b/make_post_sell/static/js/auction.js
index ff8c1d9..f81c6ae 100644
--- a/make_post_sell/static/js/auction.js
+++ b/make_post_sell/static/js/auction.js
@@ -114,9 +114,36 @@
     });
   }
 
+  // Pay-by countdown (post-end): same fmtRemaining; written into
+  // #auction-pay-countdown if present. The human deadline string is
+  // also resolved locally from the same data attribute so the user
+  // sees a consistent wall-clock + countdown in their own timezone.
+  const payCountdownEl = document.getElementById("auction-pay-countdown");
+  const payDeadlineHumanEl = document.getElementById(
+    "auction-pay-deadline-human"
+  );
+
+  function tickPayCountdown() {
+    if (!payCountdownEl) return;
+    const raw = payCountdownEl.getAttribute("data-pay-deadline");
+    if (!raw) return;
+    const deadline = parseInt(raw, 10);
+    if (isNaN(deadline)) return;
+    payCountdownEl.textContent = fmtRemaining(deadline - Date.now());
+    if (payDeadlineHumanEl && payDeadlineHumanEl.textContent === "computing…") {
+      try {
+        payDeadlineHumanEl.textContent = new Date(deadline).toLocaleString();
+      } catch (e) {
+        /* leave the placeholder */
+      }
+    }
+  }
+
   // Countdown ticks locally every second.
   setInterval(tickCountdown, 1000);
+  setInterval(tickPayCountdown, 1000);
   tickCountdown();
+  tickPayCountdown();
 
   // Live state: prefer a bounded SSE feed (the server closes it after
   // ~25s; EventSource reconnects on its own), and fall back to polling
diff --git a/make_post_sell/static/js/offer.js b/make_post_sell/static/js/offer.js
index e0c6cc3..69bcbb9 100644
--- a/make_post_sell/static/js/offer.js
+++ b/make_post_sell/static/js/offer.js
@@ -118,9 +118,46 @@
     });
   }
 
+  /* Pay-by deadline countdown.
+   *
+   * Any element carrying [data-pay-deadline] (an absolute ms timestamp)
+   * with a child .offer-pay-countdown-value will tick once a second
+   * showing how long the buyer has left to pay. When the window
+   * elapses the offer auto-expires server-side; we reflect that
+   * locally as "expired — refresh to update."
+   */
+  function fmtRemaining(ms) {
+    if (ms <= 0) return "expired";
+    var totalSeconds = Math.floor(ms / 1000);
+    var days = Math.floor(totalSeconds / 86400);
+    var hours = Math.floor((totalSeconds % 86400) / 3600);
+    var minutes = Math.floor((totalSeconds % 3600) / 60);
+    var seconds = totalSeconds % 60;
+    if (days > 0) return days + "d " + hours + "h " + minutes + "m";
+    if (hours > 0) return hours + "h " + minutes + "m " + seconds + "s";
+    if (minutes > 0) return minutes + "m " + seconds + "s";
+    return seconds + "s";
+  }
+
+  function tickPayCountdown() {
+    var nodes = document.querySelectorAll("[data-pay-deadline]");
+    if (!nodes.length) return;
+    var now = Date.now();
+    Array.prototype.forEach.call(nodes, function (node) {
+      var raw = node.getAttribute("data-pay-deadline");
+      var deadline = parseInt(raw, 10);
+      if (isNaN(deadline)) return;
+      var value = node.querySelector(".offer-pay-countdown-value");
+      if (!value) return;
+      value.textContent = fmtRemaining(deadline - now);
+    });
+  }
+
   function init() {
     wire();
     watchOfferState();
+    tickPayCountdown();
+    setInterval(tickPayCountdown, 1000);
   }
 
   if (document.readyState === "loading") {
diff --git a/make_post_sell/templates/auction.j2 b/make_post_sell/templates/auction.j2
index 06c2267..6d975a0 100644
--- a/make_post_sell/templates/auction.j2
+++ b/make_post_sell/templates/auction.j2
@@ -40,6 +40,20 @@
     {% endif %}
   </div>
 
+  {% if is_ended and user_is_winner and not is_settled and payment_deadline_timestamp %}
+  <section class="well auction-winner-pay">
+    <h3 class="type-title">You won this auction!</h3>
+    <p>
+      Complete payment by <strong id="auction-pay-deadline-human">computing&hellip;</strong>
+      <span class="js-only">&middot; <span id="auction-pay-countdown" data-pay-deadline="{{ payment_deadline_timestamp }}">computing&hellip;</span> remaining</span>,
+      or the auction will be released to the next-highest bidder.
+    </p>
+    <form method="post" action="/a/{{ id }}/checkout" class="auction-checkout-form">
+      <input type="submit" class="mps-submit mps-button-green" value="Pay ${{ '%.2f'|format(current_high) }} now" />
+    </form>
+  </section>
+  {% endif %}
+
   {% if is_active %}
     {% if user_is_seller %}
       <div class="well">
diff --git a/make_post_sell/templates/offer.j2 b/make_post_sell/templates/offer.j2
index c4c97cf..37c4eb7 100644
--- a/make_post_sell/templates/offer.j2
+++ b/make_post_sell/templates/offer.j2
@@ -107,7 +107,11 @@
           <input type="submit" class="mps-submit mps-button-green" value="Pay ${{ "%.2f"|format(current_amount) }} now" />
         </form>
         {% if pay_deadline_human %}
-        <p class="offer-pay-deadline-note">You have until <strong>{{ pay_deadline_human }}</strong> to complete payment, after which this offer auto-expires.</p>
+        <p class="offer-pay-deadline-note">You have until <strong>{{ pay_deadline_human }}</strong> to complete payment, after which this offer auto-expires.
+          {% if pay_deadline_timestamp_ms %}
+          <span class="offer-pay-countdown js-only" data-pay-deadline="{{ pay_deadline_timestamp_ms }}">&middot; <span class="offer-pay-countdown-value">computing&hellip;</span> remaining</span>
+          {% endif %}
+        </p>
         {% endif %}
         <form method="post" action="/o/{{ id }}/cancel" class="offer-cancel-form" onsubmit="return confirm('Cancel this accepted offer? You will not be able to pay this amount again unless the seller accepts a new offer.');">
           <button type="submit" class="cart-remove-link">Cancel this offer</button>
@@ -118,7 +122,11 @@
         <h3 class="type-title">Awaiting payment</h3>
         <p>You accepted <a href="/profile/{{ buyer_handle }}?shop={{ shop_id }}">{{ buyer_name }}</a>&rsquo;s offer at <strong>${{ "%.2f"|format(current_amount) }}</strong>. We emailed them a one-time checkout link &mdash; this offer can be redeemed only once.</p>
         {% if pay_deadline_human %}
-        <p class="offer-await-deadline-note">Buyer must pay by <strong>{{ pay_deadline_human }}</strong>; the offer auto-expires after that.</p>
+        <p class="offer-await-deadline-note">Buyer must pay by <strong>{{ pay_deadline_human }}</strong>; the offer auto-expires after that.
+          {% if pay_deadline_timestamp_ms %}
+          <span class="offer-pay-countdown js-only" data-pay-deadline="{{ pay_deadline_timestamp_ms }}">&middot; <span class="offer-pay-countdown-value">computing&hellip;</span> remaining</span>
+          {% endif %}
+        </p>
         {% endif %}
         <p class="offer-await-share-note">If they need it again, share this same page:</p>
         <div class="offer-pay-link-row">
diff --git a/make_post_sell/tests/test_functional.py b/make_post_sell/tests/test_functional.py
index f46d81f..c3ffdce 100644
--- a/make_post_sell/tests/test_functional.py
+++ b/make_post_sell/tests/test_functional.py
@@ -6880,6 +6880,9 @@ class TestOfferCheckout(_AuthenticatedBase):
             expires_timestamp=now_timestamp() + 86_400_000,
         )
         offer.state = OFFER_STATE_ACCEPTED
+        # Mimic accept_offer() — set accepted_timestamp so the pay-by
+        # deadline (and its JS countdown) resolves.
+        offer.accepted_timestamp = now_timestamp()
         self.dbsession.add(offer)
         self.dbsession.flush()
         offer_id = offer.uuid_str
@@ -6929,6 +6932,22 @@ class TestOfferCheckout(_AuthenticatedBase):
         # Seller never sees the buyer's pay-now form (they cannot pay).
         self.assertNotIn(f"/o/{offer_id}/checkout", body)
 
+    def test_accepted_offer_renders_pay_countdown_for_buyer(self):
+        """The buyer's accepted-offer view exposes a [data-pay-deadline]
+        countdown element with an absolute ms timestamp so offer.js can
+        tick a live "time remaining to pay" indicator. Without JS, the
+        existing static "You have until <date>" text still renders; the
+        countdown element is .js-only.
+        """
+        offer_id = self._accepted_offer()
+        self.testapp.get("/log-out")
+        self.log_in_user(self.user2_creds)
+        body = self.testapp.get(f"/o/{offer_id}", status=200).body.decode()
+        self.assertIn("Pay $75.00 now", body)
+        self.assertIn("offer-pay-countdown", body)
+        self.assertIn("data-pay-deadline=\"", body)
+        self.assertIn("offer-pay-countdown-value", body)
+
     def test_buyer_can_cancel_accepted_offer(self):
         """Buyer back-out path: POST /o/{id}/cancel flips ACCEPTED →
         BUYER_CANCELLED. The seller's accept still stands as historical
diff --git a/make_post_sell/views/auction.py b/make_post_sell/views/auction.py
index c5d4a8f..21eb814 100644
--- a/make_post_sell/views/auction.py
+++ b/make_post_sell/views/auction.py
@@ -28,6 +28,7 @@ from ..lib.currency import cents_to_dollars
 from ..models.auction import (
     AUCTION_STATE_ACTIVE,
     AUCTION_STATE_ENDED,
+    AUCTION_STATE_SETTLED,
     MpsAuction,
     MpsAuctionWatcher,
     get_auction_by_id,
@@ -93,6 +94,13 @@ def _serialize_auction(auction, request):
             and current_winning is not None
             and current_winning.bidder == request.user
         ),
+        "user_is_winner": (
+            request.user is not None
+            and auction.winner is not None
+            and auction.winner == request.user
+        ),
+        "payment_deadline_timestamp": auction.payment_deadline_timestamp,
+        "is_settled": auction.state == AUCTION_STATE_SETTLED,
     }
 
 
diff --git a/make_post_sell/views/offer.py b/make_post_sell/views/offer.py
index e0f6446..5d481fc 100644
--- a/make_post_sell/views/offer.py
+++ b/make_post_sell/views/offer.py
@@ -245,8 +245,10 @@ def offer_page(request):
         ctx["pay_deadline_human"] = datetime.fromtimestamp(
             deadline / 1000, tz=timezone.utc
         ).strftime("%Y-%m-%d %H:%M UTC")
+        ctx["pay_deadline_timestamp_ms"] = deadline
     else:
         ctx["pay_deadline_human"] = None
+        ctx["pay_deadline_timestamp_ms"] = None
     return ctx