diff --git a/src/policy/packages.h b/src/policy/packages.h
new file mode 100644
--- /dev/null
+++ b/src/policy/packages.h
@@ -0,0 +1,36 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_POLICY_PACKAGES_H
+#define BITCOIN_POLICY_PACKAGES_H
+
+#include <consensus/validation.h>
+#include <primitives/transaction.h>
+
+#include <vector>
+
+/**
+ * A "reason" why a package was invalid. It may be that one or more of the
+ * included transactions is invalid or the package itself violates our rules.
+ * We don't distinguish between consensus and policy violations right now.
+ */
+enum class PackageValidationResult {
+    //! Initial value. The package has not yet been rejected.
+    PCKG_RESULT_UNSET = 0,
+    //! The package itself is invalid (e.g. too many transactions).
+    PCKG_POLICY,
+    //! At least one tx is invalid.
+    PCKG_TX,
+};
+
+/**
+ * A package is an ordered list of transactions. The transactions cannot
+ * conflict with (spend the same inputs as) one another.
+ */
+using Package = std::vector<CTransactionRef>;
+
+class PackageValidationState : public ValidationState<PackageValidationResult> {
+};
+
+#endif // BITCOIN_POLICY_PACKAGES_H