diff --git a/certora/harness/MarketplaceHarness.sol b/certora/harness/MarketplaceHarness.sol
index 272fe9c..c2f118a 100644
--- a/certora/harness/MarketplaceHarness.sol
+++ b/certora/harness/MarketplaceHarness.sol
@@ -14,5 +14,9 @@ contract MarketplaceHarness is Marketplace {
     function requestContext(RequestId requestId) public returns (Marketplace.RequestContext memory) {
         return _requestContexts[requestId];
     }
+
+    function publicPeriodEnd(Period period) public view returns (uint256) {
+        return _periodEnd(period);
+    }
 }
 
diff --git a/certora/specs/Marketplace.spec b/certora/specs/Marketplace.spec
index 43475d6..eab3619 100644
--- a/certora/specs/Marketplace.spec
+++ b/certora/specs/Marketplace.spec
@@ -3,6 +3,7 @@ using ERC20A as Token;
 methods {
     function Token.balanceOf(address) external returns (uint256) envfree;
     function Token.totalSupply() external returns (uint256) envfree;
+    function publicPeriodEnd(Periods.Period) external returns (uint256) envfree;
 }
 
 /*--------------------------------------------
@@ -41,6 +42,27 @@ hook Sstore currentContract._marketplaceTotals.sent uint256 defaultValue (uint25
     totalSent = totalSent + defaultValue - defaultValue_old;
 }
 
+ghost uint256 lastBlockTimestampGhost;
+
+hook TIMESTAMP uint v {
+    require lastBlockTimestampGhost <= v;
+    lastBlockTimestampGhost = v;
+}
+
+ghost mapping(MarketplaceHarness.SlotId => mapping(Periods.Period => bool)) _missingMirror {
+    init_state axiom forall MarketplaceHarness.SlotId a. 
+            forall Periods.Period b. 
+            _missingMirror[a][b] == false;
+}
+
+hook Sload bool defaultValue _missing[KEY MarketplaceHarness.SlotId slotId][KEY Periods.Period period] {
+    require _missingMirror[slotId][period] == defaultValue;
+}
+
+hook Sstore _missing[KEY MarketplaceHarness.SlotId slotId][KEY Periods.Period period] bool defaultValue {
+    _missingMirror[slotId][period] = defaultValue;
+}
+
 /*--------------------------------------------
 |              Helper functions              |
 --------------------------------------------*/
@@ -72,6 +94,12 @@ invariant totalSupplyIsSumOfBalances()
 invariant requestStartedWhenSlotsFilled(env e, Marketplace.RequestId requestId, Marketplace.SlotId slotId)
     to_mathint(currentContract.requestContext(e, requestId).slotsFilled) == to_mathint(currentContract.getRequest(e, requestId).ask.slots) => currentContract.requestState(e, requestId) == Marketplace.RequestState.Started;
 
+// STATUS - verified
+// can set missing if period was passed
+// https://prover.certora.com/output/3106/026b36c118e44ad0824a51c50647c497/?anonymousKey=29879706f3d343555bb6122d071c9409d4e9876d
+invariant cantBeMissedIfInPeriod(MarketplaceHarness.SlotId slotId, Periods.Period period)
+    lastBlockTimestampGhost <= publicPeriodEnd(period) => !_missingMirror[slotId][period];
+
 /*--------------------------------------------
 |                 Properties                 |
 --------------------------------------------*/