Changed the budgets helper so just search for the current budget

app/helpers/budgets_helper.rb

@@ -52,8 +52,8 @@ module BudgetsHelper
     Budget::Ballot.where(user: current_user, budget: @budget).first
   end
 
-  def investment_tags_select_options
-    Budget::Investment.tags_on(:valuation).order(:name).select(:name).distinct
+  def investment_tags_select_options(budget)
+    Budget::Investment.where(budget_id: budget).tags_on(:valuation).order(:name).select(:name).distinct
   end
 
   def budget_published?(budget)

app/views/admin/budget_investments/index.html.erb

@@ -25,14 +25,15 @@
                      class: "js-submit-on-change" } %>
   </div>
 
-  <div class="small-12 medium-3 column">
-    <%= select_tag :tag_name,
-                   options_for_select(investment_tags_select_options, params[:tag_name]),
-                   { prompt: t("admin.budget_investments.index.tags_filter_all"),
-                     label: false,
-                     class: "js-submit-on-change" } %>
-  </div>
-<% end %>
+    <div class="small-12 medium-3 column">
+      <%= select_tag :tag_name,
+                     options_for_select(investment_tags_select_options(@budget), params[:tag_name]),
+                     { prompt: t("admin.budget_investments.index.tags_filter_all"),
+                       label: false,
+                       class: "js-submit-on-change" } %>
+    </div>
+  <% end %>
+</div>
 
 <%= render "advanced_filters", i18n_namespace: "admin.budget_investments.index" %>