diff --git a/app/assets/stylesheets/components/_sweetalert.scss b/app/assets/stylesheets/components/_sweetalert.scss
index e864621094..7ef8274f57 100644
--- a/app/assets/stylesheets/components/_sweetalert.scss
+++ b/app/assets/stylesheets/components/_sweetalert.scss
@@ -48,6 +48,17 @@
     background-color: transparent;
   }
 
+  .swal-content {
+    input {
+      color: inherit;
+      background: transparent;
+      border: 1px solid rgba(150, 150, 150, 0.4);
+      border-radius: var(--radius-md, 6px);
+      padding: 8px 12px;
+      width: 100%;
+    }
+  }
+
   .swal-button {
     @extend .btn;
   }
diff --git a/app/controllers/admin_controller.rb b/app/controllers/admin_controller.rb
index 4f6308e7e9..a894009ce3 100644
--- a/app/controllers/admin_controller.rb
+++ b/app/controllers/admin_controller.rb
@@ -55,6 +55,17 @@ def transaction
                            elsif @canonical_transaction.amount_cents.abs >= 5_000_00 # $5k
                              "Are you really really sure you want to map this transaction? 🤔 it seems like a big one :)"
                            end
+
+    # If this transaction was already mapped a while ago, remapping it annoys Sierra's accounting system.
+
+    if @canonical_transaction.canonical_event_mapping.present? &&
+       @canonical_transaction.canonical_event_mapping.created_at < 12.hours.ago
+      @stale_remap = true
+      @remap_confirm_msg = "⚠️ This transaction was already mapped to \"#{@canonical_transaction.event&.name}\" #{helpers.time_ago_in_words(@canonical_transaction.canonical_event_mapping.created_at)} ago. Remapping it now may disrupt our accounting. Are you absolutely sure you want to remap this transaction?"
+      @remap_confirm_phrase = "REMAP #{@canonical_transaction.id}"
+      @remap_after_message = "Please contact Sierra and the HCB Ops team right away to let them know you remapped transaction ##{@canonical_transaction.id}."
+      @remap_warning_tooltip = "This transaction was already mapped #{helpers.time_ago_in_words(@canonical_transaction.canonical_event_mapping.created_at)} ago — remapping it requires extra confirmation."
+    end
   end
 
   def events
diff --git a/app/javascript/confirm.js b/app/javascript/confirm.js
index c412cb7f18..0f534e3393 100644
--- a/app/javascript/confirm.js
+++ b/app/javascript/confirm.js
@@ -13,14 +13,69 @@ function showConfirm(
   }).then(v => !!v)
 }
 
+async function showTypeToConfirm(
+  message,
+  phrase,
+  { title = 'Are you sure?', afterMessage = null } = {}
+) {
+  const warned = await swal({
+    title,
+    text: message,
+    icon: 'warning',
+    buttons: ['Cancel', "Yes, I'm sure"],
+    dangerMode: true,
+  })
+  if (!warned) return false
+
+  const typed = await swal({
+    title: 'Confirm by typing',
+    text: `Type "${phrase}" below to confirm:`,
+    content: {
+      element: 'input',
+      attributes: {
+        placeholder: phrase,
+        type: 'text',
+      },
+    },
+    buttons: ['Cancel', 'Confirm'],
+    dangerMode: true,
+  })
+  if (typed?.trim() !== phrase) {
+    if (typed !== null) {
+      await swal('Not confirmed', 'What you typed did not match.', 'error')
+    }
+    return false
+  }
+
+  if (afterMessage) {
+    await swal('One more thing', afterMessage, 'info')
+  }
+
+  return true
+}
+
 Turbo.config.forms.confirm = (message, formElement, submitter) => {
   const dangerMode = Boolean(
     submitter?.hasAttribute('data-turbo-confirm-danger') ||
     formElement?.hasAttribute('data-turbo-confirm-danger')
   )
+
+  const phrase =
+    submitter?.getAttribute('data-turbo-confirm-type-phrase') ||
+    formElement?.getAttribute('data-turbo-confirm-type-phrase')
+
+  if (phrase) {
+    const afterMessage =
+      submitter?.getAttribute('data-turbo-confirm-after-message') ||
+      formElement?.getAttribute('data-turbo-confirm-after-message')
+
+    return showTypeToConfirm(message, phrase, { afterMessage })
+  }
+
   return showConfirm(message, { dangerMode })
 }
 window.showConfirm = showConfirm
+window.showTypeToConfirm = showTypeToConfirm
 window.swal = swal
 
 export default showConfirm
diff --git a/app/views/admin/transaction.html.erb b/app/views/admin/transaction.html.erb
index cbfdb4b96c..03544470fb 100644
--- a/app/views/admin/transaction.html.erb
+++ b/app/views/admin/transaction.html.erb
@@ -2,6 +2,13 @@
 
 <h1>Transaction <%= @canonical_transaction.id %></h1>
 
+<% remap_confirm_data = @stale_remap ? {
+     "turbo-confirm-danger": true,
+     "turbo-confirm-type-phrase": @remap_confirm_phrase,
+     "turbo-confirm-after-message": @remap_after_message,
+   } : {} %>
+<% remap_warning_icon = @stale_remap ? content_tag(:span, "⚠️", class: "tooltipped tooltipped--n ml-1", style: "cursor: help;", "aria-label": @remap_warning_tooltip) : "".html_safe %>
+
 <table class="no-stripes <%= "admin-bg-pending" unless @canonical_transaction.canonical_event_mapping %>">
   <tbody>
     <tr>
@@ -85,7 +92,8 @@
         <div class="flex flex-row gap-2">
           <%= form_with model: false, local: true, url: set_event_path(@canonical_transaction), method: :post do |form| %>
             <%= combobox_tag :event_id, event_search_admin_index_path, placeholder: "Select event", class: "!max-w-full !min-w-72", value: @canonical_transaction.event&.to_combobox_display %>
-            <%= form.submit "Set", data: { "turbo-confirm": @mapping_confirm_msg } %>
+            <%= form.submit "Set", data: remap_confirm_data.merge("turbo-confirm": @stale_remap ? @remap_confirm_msg : @mapping_confirm_msg) %>
+            <%= remap_warning_icon %>
           <% end %>
         </div>
         <%= form_with url: set_event_path(@canonical_transaction), method: :post do |form| %>