diff --git a/boat-quay/boat-quay-rules/src/main/kotlin/com/backbase/oss/boat/quay/ruleset/InfoBlockSunsetDateChecker.kt b/boat-quay/boat-quay-rules/src/main/kotlin/com/backbase/oss/boat/quay/ruleset/InfoBlockSunsetDateChecker.kt
new file mode 100644
index 000000000..0d0fa13a6
--- /dev/null
+++ b/boat-quay/boat-quay-rules/src/main/kotlin/com/backbase/oss/boat/quay/ruleset/InfoBlockSunsetDateChecker.kt
@@ -0,0 +1,74 @@
+package com.backbase.oss.boat.quay.ruleset
+
+import org.zalando.zally.core.toJsonPointer
+import org.zalando.zally.rule.api.*
+import java.time.LocalDate
+import java.time.format.DateTimeFormatter
+import java.time.format.DateTimeParseException
+
+@Rule(
+    ruleSet = BoatRuleSet::class,
+    id = "B015",
+    severity = Severity.MUST,
+    title = "Check x-sunset-date is set and valid when x-deprecated is true"
+)
+class InfoBlockSunsetDateChecker {
+
+    @Check(Severity.MUST)
+    fun validate(context: Context): List<Violation> {
+        val violations = mutableListOf<Violation>()
+        val extensions = context.api.info.extensions ?: return emptyList()
+
+        val isDeprecated = isTrue(extensions["x-deprecated"])
+        val sunsetDateValue = extensions["x-sunset-date"]
+        val hasSunsetDate = sunsetDateValue != null && sunsetDateValue.toString().isNotBlank()
+
+        when {
+            isDeprecated && !hasSunsetDate -> {
+                violations.add(
+                    context.violation(
+                        "x-sunset-date must be set (as YYYY-MM-DD) when x-deprecated is true",
+                        "/openapi/info/x-sunset-date".toJsonPointer()
+                    )
+                )
+            }
+            isDeprecated && hasSunsetDate -> {
+                if (!isValidDate(sunsetDateValue.toString())) {
+                    violations.add(
+                        context.violation(
+                            "x-sunset-date must be a valid YYYY-MM-DD date, got: ${sunsetDateValue}",
+                            "/openapi/info/x-sunset-date".toJsonPointer()
+                        )
+                    )
+                }
+            }
+            !isDeprecated && hasSunsetDate -> {
+                violations.add(
+                    context.violation(
+                        "x-sunset-date is set but x-deprecated is not true — remove the stale sunset date or mark the API deprecated",
+                        "/openapi/info/x-sunset-date".toJsonPointer()
+                    )
+                )
+            }
+        }
+
+        return violations
+    }
+
+    private fun isTrue(value: Any?): Boolean {
+        return when (value) {
+            is Boolean -> value
+            is String -> value.equals("true", ignoreCase = true)
+            else -> false
+        }
+    }
+
+    private fun isValidDate(value: String): Boolean {
+        return try {
+            LocalDate.parse(value, DateTimeFormatter.ISO_LOCAL_DATE)
+            true
+        } catch (e: DateTimeParseException) {
+            false
+        }
+    }
+}
diff --git a/boat-quay/boat-quay-rules/src/test/kotlin/com/backbase/oss/boat/quay/ruleset/InfoBlockSunsetDateCheckerTest.kt b/boat-quay/boat-quay-rules/src/test/kotlin/com/backbase/oss/boat/quay/ruleset/InfoBlockSunsetDateCheckerTest.kt
new file mode 100644
index 000000000..5d85ed1e3
--- /dev/null
+++ b/boat-quay/boat-quay-rules/src/test/kotlin/com/backbase/oss/boat/quay/ruleset/InfoBlockSunsetDateCheckerTest.kt
@@ -0,0 +1,193 @@
+package com.backbase.oss.boat.quay.ruleset
+
+import com.backbase.oss.boat.quay.ruleset.test.ZallyAssertions
+import org.intellij.lang.annotations.Language
+import org.junit.jupiter.api.Test
+import org.zalando.zally.core.DefaultContextFactory
+
+class InfoBlockSunsetDateCheckerTest {
+
+    private val cut = InfoBlockSunsetDateChecker()
+
+    @Test
+    fun `x-deprecated true with valid x-sunset-date passes`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+              x-deprecated: true
+              x-sunset-date: "2027-04-15"
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isEmpty()
+    }
+
+    @Test
+    fun `x-deprecated true without x-sunset-date fails`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+              x-deprecated: true
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isNotEmpty
+    }
+
+    @Test
+    fun `x-deprecated true with empty x-sunset-date fails`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+              x-deprecated: true
+              x-sunset-date: ""
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isNotEmpty
+    }
+
+    @Test
+    fun `x-deprecated true with malformed x-sunset-date fails`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+              x-deprecated: true
+              x-sunset-date: "2027.04"
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isNotEmpty
+    }
+
+    @Test
+    fun `x-deprecated false without x-sunset-date passes`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+              x-deprecated: false
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isEmpty()
+    }
+
+    @Test
+    fun `no x-deprecated without x-sunset-date passes`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isEmpty()
+    }
+
+    @Test
+    fun `x-deprecated false with x-sunset-date fails`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+              x-deprecated: false
+              x-sunset-date: "2027-04-15"
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isNotEmpty
+    }
+
+    @Test
+    fun `no x-deprecated with x-sunset-date fails`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+              x-sunset-date: "2027-04-15"
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isNotEmpty
+    }
+
+    @Test
+    fun `no extensions passes`() {
+        @Language("YAML")
+        val context = DefaultContextFactory().getOpenApiContext(
+            """
+            openapi: 3.0.3
+            info:
+              title: API
+              version: 1.0.0
+            """.trimIndent()
+        )
+
+        val violations = cut.validate(context)
+
+        ZallyAssertions
+            .assertThat(violations)
+            .isEmpty()
+    }
+}