diff --git a/app/models/budget.rb b/app/models/budget.rb
index 560a5f17..134258ca 100644
--- a/app/models/budget.rb
+++ b/app/models/budget.rb
@@ -133,10 +133,10 @@ class Budget < ApplicationRecord
   end
 
   # =============================================================================
-  # Budget allocations: How much user has budgeted for all categories combined
+  # Budget allocations: How much user has budgeted for all parent categories combined
   # =============================================================================
   def allocated_spending
-    budget_categories.sum(:budgeted_spending)
+    budget_categories.reject { |bc| bc.subcategory? }.sum(&:budgeted_spending)
   end
 
   def allocated_percent
diff --git a/app/models/budget_category.rb b/app/models/budget_category.rb
index a57a3a97..5109198d 100644
--- a/app/models/budget_category.rb
+++ b/app/models/budget_category.rb
@@ -79,4 +79,29 @@ class BudgetCategory < ApplicationRecord
 
     segments
   end
+
+  def siblings
+    budget.budget_categories.select { |bc| bc.category.parent_id == category.parent_id && bc.id != id }
+  end
+
+  def max_allocation
+    return nil unless subcategory?
+
+    parent_budget = budget.budget_categories.find { |bc| bc.category.id == category.parent_id }&.budgeted_spending
+    siblings_budget = siblings.sum(&:budgeted_spending)
+
+    [ parent_budget - siblings_budget, 0 ].max
+  end
+
+  def subcategories
+    return BudgetCategory.none unless category.parent_id.nil?
+
+    budget.budget_categories
+      .joins(:category)
+      .where(categories: { parent_id: category.id })
+  end
+
+  def subcategory?
+    category.parent_id.present?
+  end
 end
diff --git a/app/views/budget_categories/_budget_category_form.html.erb b/app/views/budget_categories/_budget_category_form.html.erb
index 770d6293..08fd70e0 100644
--- a/app/views/budget_categories/_budget_category_form.html.erb
+++ b/app/views/budget_categories/_budget_category_form.html.erb
@@ -2,7 +2,7 @@
 
 <% currency = Money::Currency.new(budget_category.budget.currency) %>
 
-<div class="w-full flex gap-3">
+<div id=<%= dom_id(budget_category, :form) %> class="w-full flex gap-3">
   <div class="w-1 h-3 rounded-xl mt-1" style="background-color: <%= budget_category.category.color %>"></div>
 
   <div class="text-sm mr-3">
@@ -22,6 +22,7 @@
                             step: currency.step,
                             id: dom_id(budget_category, :budgeted_spending),
                             min: 0,
+                            max: budget_category.max_allocation,
                             data: { auto_submit_form_target: "auto" } %>
         </div>
       </div>
diff --git a/app/views/budget_categories/_confirm_button.html.erb b/app/views/budget_categories/_confirm_button.html.erb
new file mode 100644
index 00000000..53c52533
--- /dev/null
+++ b/app/views/budget_categories/_confirm_button.html.erb
@@ -0,0 +1,11 @@
+<div id="<%= dom_id(budget, :confirm_button) %>">
+  <% if budget.allocations_valid? %>
+    <%= link_to "Confirm",
+        budget_path(budget),
+        class: "block btn btn--primary w-full text-center" %>
+  <% else %>
+    <span class="block btn btn--secondary w-full text-center text-gray-400 cursor-not-allowed">
+      Confirm
+    </span>
+  <% end %>
+</div>
\ No newline at end of file
diff --git a/app/views/budget_categories/_uncategorized_budget_category_form.html.erb b/app/views/budget_categories/_uncategorized_budget_category_form.html.erb
index 4e586379..f26a9f80 100644
--- a/app/views/budget_categories/_uncategorized_budget_category_form.html.erb
+++ b/app/views/budget_categories/_uncategorized_budget_category_form.html.erb
@@ -2,7 +2,7 @@
 
 <% budget_category = budget.uncategorized_budget_category %>
 
-<div class="flex gap-3">
+<div id="<%= dom_id(budget, :uncategorized_budget_category_form) %>" class="flex gap-3">
   <div class="w-1 h-3 rounded-xl mt-1" style="background-color: <%= budget_category.category.color %>"></div>
 
   <div class="text-sm mr-3">
diff --git a/app/views/budget_categories/index.html.erb b/app/views/budget_categories/index.html.erb
index f40879de..1ae9ea97 100644
--- a/app/views/budget_categories/index.html.erb
+++ b/app/views/budget_categories/index.html.erb
@@ -45,15 +45,7 @@
             <%= render "budget_categories/uncategorized_budget_category_form", budget: @budget %>
           </div>
 
-          <% if @budget.allocations_valid? %>
-            <%= link_to "Confirm",
-                budget_path(@budget),
-                class: "block btn btn--primary w-full text-center" %>
-          <% else %>
-            <span class="block btn btn--secondary w-full text-center text-gray-400 cursor-not-allowed">
-              Confirm
-            </span>
-          <% end %>
+        <%= render "budget_categories/confirm_button", budget: @budget %>
         </div>
       <% end %>
     </div>
diff --git a/app/views/budget_categories/update.turbo_stream.erb b/app/views/budget_categories/update.turbo_stream.erb
index 31a70c51..34313156 100644
--- a/app/views/budget_categories/update.turbo_stream.erb
+++ b/app/views/budget_categories/update.turbo_stream.erb
@@ -1 +1,19 @@
 <%= turbo_stream.replace dom_id(@budget, :allocation_progress), partial: "budget_categories/allocation_progress", locals: { budget: @budget } %>
+
+<%= turbo_stream.replace dom_id(@budget, :uncategorized_budget_category_form), partial: "budget_categories/uncategorized_budget_category_form", locals: { budget: @budget } %>
+
+<%= turbo_stream.replace dom_id(@budget, :confirm_button), partial: "budget_categories/confirm_button", locals: { budget: @budget } %>
+
+
+<% if @budget_category.subcategory? %>
+  <%# Update sibling subcategories when a subcategory changes %>
+  <% @budget_category.siblings.each do |sibling| %>
+    <%= turbo_stream.update dom_id(sibling, :form), partial: "budget_categories/budget_category_form", locals: { budget_category: sibling } %>
+  <% end %>
+  
+<% else %>
+  <%# Update all subcategories when a parent category changes %>
+  <% @budget_category.subcategories.each do |subcategory| %>
+    <%= turbo_stream.update dom_id(subcategory, :form), partial: "budget_categories/budget_category_form", locals: { budget_category: subcategory } %>
+  <% end %>
+<% end %>
\ No newline at end of file