diff --git a/src/EntitlementPushContract.php b/src/EntitlementPushContract.php
new file mode 100644
index 0000000..4863f82
--- /dev/null
+++ b/src/EntitlementPushContract.php
@@ -0,0 +1,84 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Novvor\CentralSdk;
+
+use InvalidArgumentException;
+
+/** Shared canonical contract for Central's signed v1 entitlement push endpoint. */
+final class EntitlementPushContract
+{
+    /** @param array<string, mixed> $payload */
+    public static function canonicalJson(array $payload): string
+    {
+        return json_encode(
+            self::canonicalPayload($payload),
+            JSON_THROW_ON_ERROR | JSON_UNESCAPED_SLASHES,
+        );
+    }
+
+    /**
+     * @param array<string, mixed> $payload
+     * @return array<string, mixed>
+     */
+    public static function canonicalPayload(array $payload): array
+    {
+        self::assertValid($payload);
+        $limits = (array) $payload['limits'];
+
+        return [
+            'tenant_id' => (string) $payload['tenant_id'],
+            'tenant_ref' => [
+                'issuer' => (string) $payload['tenant_ref']['issuer'],
+                'id' => (string) $payload['tenant_ref']['id'],
+            ],
+            'product_code' => (string) $payload['product_code'],
+            'sku_code' => (string) $payload['sku_code'],
+            'version' => (int) $payload['version'],
+            'modules' => $payload['modules'],
+            'capabilities' => $payload['capabilities'],
+            'limits' => $limits === [] ? (object) [] : $limits,
+            'addons' => $payload['addons'],
+        ];
+    }
+
+    /** @param array<string, mixed> $payload */
+    public static function assertValid(array $payload): void
+    {
+        foreach (
+            [
+                'tenant_id', 'tenant_ref', 'product_code', 'sku_code', 'version',
+                'modules', 'capabilities', 'limits', 'addons',
+            ] as $field
+        ) {
+            if (! array_key_exists($field, $payload)) {
+                throw new InvalidArgumentException("Central entitlement push is missing {$field}.");
+            }
+        }
+
+        foreach (['tenant_id', 'product_code', 'sku_code'] as $field) {
+            if (! is_string($payload[$field]) || trim($payload[$field]) === '') {
+                throw new InvalidArgumentException("Central entitlement push {$field} is invalid.");
+            }
+        }
+
+        if (
+            ! is_array($payload['tenant_ref'])
+            || ($payload['tenant_ref']['issuer'] ?? null) !== 'central'
+            || ($payload['tenant_ref']['id'] ?? null) !== $payload['tenant_id']
+        ) {
+            throw new InvalidArgumentException('Central entitlement push tenant reference is invalid.');
+        }
+
+        if (! is_int($payload['version']) || $payload['version'] < 1) {
+            throw new InvalidArgumentException('Central entitlement push version is invalid.');
+        }
+
+        foreach (['modules', 'capabilities', 'limits', 'addons'] as $field) {
+            if (! is_array($payload[$field]) && ! is_object($payload[$field])) {
+                throw new InvalidArgumentException("Central entitlement push {$field} is invalid.");
+            }
+        }
+    }
+}
diff --git a/tests/EntitlementPushContractTest.php b/tests/EntitlementPushContractTest.php
new file mode 100644
index 0000000..b136c95
--- /dev/null
+++ b/tests/EntitlementPushContractTest.php
@@ -0,0 +1,69 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Novvor\CentralSdk\Tests;
+
+use InvalidArgumentException;
+use Novvor\CentralSdk\EntitlementPushContract;
+use PHPUnit\Framework\TestCase;
+
+final class EntitlementPushContractTest extends TestCase
+{
+    public function test_empty_limit_map_survives_a_wire_json_round_trip(): void
+    {
+        $wirePayload = $this->payload();
+        $wirePayload['limits'] = (object) [];
+        $decodedPayload = json_decode(
+            json_encode($wirePayload, JSON_THROW_ON_ERROR),
+            true,
+            512,
+            JSON_THROW_ON_ERROR,
+        );
+
+        $canonical = EntitlementPushContract::canonicalJson($wirePayload);
+
+        self::assertSame($canonical, EntitlementPushContract::canonicalJson($decodedPayload));
+        self::assertStringContainsString('"limits":{}', $canonical);
+    }
+
+    public function test_tenant_reference_is_signed_and_must_match_the_subject(): void
+    {
+        $payload = $this->payload();
+        $payload['tenant_ref']['id'] = 'another-tenant';
+
+        $this->expectException(InvalidArgumentException::class);
+        EntitlementPushContract::canonicalJson($payload);
+    }
+
+    public function test_canonical_field_order_is_stable_and_excludes_transport_metadata(): void
+    {
+        $payload = $this->payload();
+        $payload['snapshot_hash'] = str_repeat('a', 64);
+        $payload['generated_at'] = '2026-08-22T00:00:00Z';
+
+        self::assertSame(
+            [
+                'tenant_id', 'tenant_ref', 'product_code', 'sku_code', 'version',
+                'modules', 'capabilities', 'limits', 'addons',
+            ],
+            array_keys(EntitlementPushContract::canonicalPayload($payload)),
+        );
+    }
+
+    /** @return array<string, mixed> */
+    private function payload(): array
+    {
+        return [
+            'tenant_id' => 'tenant-1',
+            'tenant_ref' => ['issuer' => 'central', 'id' => 'tenant-1'],
+            'product_code' => 'filasign',
+            'sku_code' => 'none',
+            'version' => 20260822000101,
+            'modules' => [],
+            'capabilities' => [],
+            'limits' => ['envelopes_per_month' => 25],
+            'addons' => [],
+        ];
+    }
+}