diff --git a/src/components/Community.tsx b/src/components/Community.tsx
index 4f72391..8625ac4 100644
--- a/src/components/Community.tsx
+++ b/src/components/Community.tsx
@@ -1,5 +1,5 @@
 import React, { useState, useEffect, useRef, useCallback } from 'react';
-import { Search, Globe, Users, Eye, ArrowLeftRight, Loader2, Clock, History, UserPlus, UserMinus, Check, X, Send, Settings, Save, ChevronLeft, RefreshCw, Plus, Minus } from 'lucide-react';
+import { Search, Globe, Users, Eye, ArrowLeftRight, Loader2, Clock, History, UserPlus, UserMinus, Check, X, Send, Settings, Save, ChevronLeft, RefreshCw, Plus, Minus, AlertTriangle } from 'lucide-react';
 import { useAuth } from '../contexts/AuthContext';
 import { useToast } from '../contexts/ToastContext';
 import { supabase } from '../lib/supabase';
@@ -1412,9 +1412,14 @@ export default function Community() {
                             With: <strong>{otherUser?.username}</strong>
                           </span>
                         </div>
-                        <span className={`text-xs capitalize ${statusColors[trade.status]}`}>
-                          {trade.status}
-                        </span>
+                        <div className="flex items-center gap-1.5">
+                          {trade.status === 'pending' && !trade.is_valid && (
+                            <AlertTriangle size={14} className="text-red-400" title="Trade no longer valid" />
+                          )}
+                          <span className={`text-xs capitalize ${statusColors[trade.status]}`}>
+                            {trade.status}
+                          </span>
+                        </div>
                       </div>
 
                       {/* Items */}
diff --git a/src/components/TradeDetail.tsx b/src/components/TradeDetail.tsx
index efb6b1c..cc7a26b 100644
--- a/src/components/TradeDetail.tsx
+++ b/src/components/TradeDetail.tsx
@@ -1,5 +1,5 @@
 import React, { useState, useEffect } from 'react';
-import { X, Check, ArrowLeftRight, DollarSign, Loader2, Edit, RefreshCcw, History } from 'lucide-react';
+import { X, Check, ArrowLeftRight, DollarSign, Loader2, Edit, RefreshCcw, History, AlertTriangle } from 'lucide-react';
 import { useAuth } from '../contexts/AuthContext';
 import { useToast } from '../contexts/ToastContext';
 import { Trade, TradeHistoryEntry, getTradeVersionHistory } from '../services/tradesService';
@@ -222,6 +222,18 @@ export default function TradeDetail({
             </div>
           ) : (
             <div className="space-y-4">
+              {/* Invalid Trade Warning */}
+              {trade.status === 'pending' && !trade.is_valid && (
+                <div className="bg-red-900/30 border border-red-600 rounded-lg p-3 flex items-start gap-2">
+                  <AlertTriangle size={20} className="text-red-400 flex-shrink-0 mt-0.5" />
+                  <div>
+                    <h4 className="font-semibold text-red-400 text-sm">Trade No Longer Valid</h4>
+                    <p className="text-red-200 text-xs mt-1">
+                      One or more cards in this trade are no longer available in the required quantities. This trade cannot be accepted until it is updated.
+                    </p>
+                  </div>
+                </div>
+              )}
               <div className="grid grid-cols-1 lg:grid-cols-2 gap-4">
                 {/* Your Side */}
                 <div className="space-y-3">
@@ -367,8 +379,9 @@ export default function TradeDetail({
                 <div className="flex gap-2">
                   <button
                     onClick={handleAccept}
-                    disabled={processing}
-                    className="flex-1 flex items-center justify-center gap-2 px-4 py-3 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 rounded-lg font-medium transition"
+                    disabled={processing || !trade.is_valid}
+                    className="flex-1 flex items-center justify-center gap-2 px-4 py-3 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg font-medium transition"
+                    title={!trade.is_valid ? 'This trade is no longer valid' : ''}
                   >
                     {processing ? (
                       <Loader2 className="animate-spin" size={18} />
@@ -431,8 +444,9 @@ export default function TradeDetail({
                     <div className="flex gap-2">
                       <button
                         onClick={handleAccept}
-                        disabled={processing}
-                        className="flex-1 flex items-center justify-center gap-2 px-4 py-3 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 rounded-lg font-medium transition"
+                        disabled={processing || !trade.is_valid}
+                        className="flex-1 flex items-center justify-center gap-2 px-4 py-3 bg-green-600 hover:bg-green-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg font-medium transition"
+                        title={!trade.is_valid ? 'This trade is no longer valid' : ''}
                       >
                         {processing ? (
                           <Loader2 className="animate-spin" size={18} />
diff --git a/src/services/tradesService.ts b/src/services/tradesService.ts
index d4d31f5..773e04d 100644
--- a/src/services/tradesService.ts
+++ b/src/services/tradesService.ts
@@ -18,6 +18,7 @@ export interface Trade {
   updated_at: string | null;
   version: number;
   editor_id: string | null;
+  is_valid: boolean;
   user1?: { username: string | null };
   user2?: { username: string | null };
   items?: TradeItem[];
@@ -160,6 +161,25 @@ export async function createTrade(params: CreateTradeParams): Promise<Trade> {
 
 // Accept a trade (executes the card transfer)
 export async function acceptTrade(tradeId: string): Promise<boolean> {
+  // First check if the trade is valid
+  const { data: trade, error: tradeError } = await supabase
+    .from('trades')
+    .select('is_valid, status')
+    .eq('id', tradeId)
+    .single();
+
+  if (tradeError) throw tradeError;
+
+  // Prevent accepting invalid trades
+  if (!trade.is_valid) {
+    throw new Error('This trade is no longer valid. One or more cards are no longer available in the required quantities.');
+  }
+
+  // Prevent accepting non-pending trades
+  if (trade.status !== 'pending') {
+    throw new Error('This trade has already been processed.');
+  }
+
   const { data, error } = await supabase.rpc('execute_trade', {
     trade_id: tradeId,
   });
diff --git a/supabase/migrations/20250127000001_add_trade_validation.sql b/supabase/migrations/20250127000001_add_trade_validation.sql
new file mode 100644
index 0000000..8aba551
--- /dev/null
+++ b/supabase/migrations/20250127000001_add_trade_validation.sql
@@ -0,0 +1,101 @@
+-- Add is_valid column to trades table
+ALTER TABLE public.trades
+ADD COLUMN IF NOT EXISTS is_valid BOOLEAN DEFAULT true;
+
+-- Create index for filtering by validity
+CREATE INDEX IF NOT EXISTS idx_trades_is_valid ON public.trades(is_valid);
+
+-- Function to validate if a trade can still be executed based on current collections
+CREATE OR REPLACE FUNCTION public.validate_trade(p_trade_id uuid)
+RETURNS boolean
+LANGUAGE plpgsql
+SECURITY DEFINER
+AS $$
+DECLARE
+  v_item RECORD;
+  v_collection_quantity integer;
+BEGIN
+  -- Check each item in the trade
+  FOR v_item IN
+    SELECT owner_id, card_id, quantity
+    FROM public.trade_items
+    WHERE trade_id = p_trade_id
+  LOOP
+    -- Get the quantity of this card in the owner's collection
+    SELECT COALESCE(quantity, 0) INTO v_collection_quantity
+    FROM public.collections
+    WHERE user_id = v_item.owner_id
+    AND card_id = v_item.card_id;
+
+    -- If owner doesn't have enough of this card, trade is invalid
+    IF v_collection_quantity < v_item.quantity THEN
+      RETURN false;
+    END IF;
+  END LOOP;
+
+  -- All items are available, trade is valid
+  RETURN true;
+END;
+$$;
+
+-- Function to check and update validity of affected trades when collections change
+CREATE OR REPLACE FUNCTION public.update_affected_trades_validity()
+RETURNS TRIGGER
+LANGUAGE plpgsql
+SECURITY DEFINER
+AS $$
+DECLARE
+  v_user_id uuid;
+  v_card_id text;
+  v_trade RECORD;
+  v_is_valid boolean;
+BEGIN
+  -- Get the user_id and card_id from the changed row
+  IF (TG_OP = 'DELETE') THEN
+    v_user_id := OLD.user_id;
+    v_card_id := OLD.card_id;
+  ELSE
+    v_user_id := NEW.user_id;
+    v_card_id := NEW.card_id;
+  END IF;
+
+  -- Find all pending trades that involve this card from this user
+  FOR v_trade IN
+    SELECT DISTINCT t.id
+    FROM public.trades t
+    JOIN public.trade_items ti ON ti.trade_id = t.id
+    WHERE t.status = 'pending'
+    AND ti.owner_id = v_user_id
+    AND ti.card_id = v_card_id
+  LOOP
+    -- Validate the trade
+    v_is_valid := public.validate_trade(v_trade.id);
+
+    -- Update the trade's validity
+    UPDATE public.trades
+    SET is_valid = v_is_valid,
+        updated_at = now()
+    WHERE id = v_trade.id;
+  END LOOP;
+
+  IF (TG_OP = 'DELETE') THEN
+    RETURN OLD;
+  ELSE
+    RETURN NEW;
+  END IF;
+END;
+$$;
+
+-- Create trigger to auto-update trade validity when collections change
+CREATE TRIGGER update_trades_on_collection_change
+AFTER UPDATE OR DELETE ON public.collections
+FOR EACH ROW
+EXECUTE FUNCTION public.update_affected_trades_validity();
+
+-- Add comment
+COMMENT ON COLUMN public.trades.is_valid IS 'Indicates if the trade can still be executed based on current collections. Auto-updated when collections change.';
+
+-- Initial validation: set is_valid for all existing pending trades
+UPDATE public.trades
+SET is_valid = public.validate_trade(id)
+WHERE status = 'pending';