diff --git a/README.md b/README.md
index 55b1b85295..e0b71bee23 100644
--- a/README.md
+++ b/README.md
@@ -211,21 +211,15 @@ diktat {
 }
 ```
 
-Also `diktat` extension has different reporters. You can specify `json`, `html`, `sarif`, `plain` (default) or your own custom reporter (it should be added as a dependency into `diktat` configuration):
+Also in `diktat` extension you can configure different reporters and their output. You can specify `json`, `html`, `sarif`, `plain` (default).
+If `output` is set, it should be a file path. If not set, results will be printed to stdout.
 ```kotlin
 diktat {
     // since 1.2.1 to keep in line with maven properties
     reporter = "json" // "html", "json", "plain" (default), "sarif"
     // before 1.2.1
     // reporterType = "json" // "html", "json", "plain" (default), "sarif"
-}
-```
 
-You can also specify an output.
-```kotlin
-diktat {
-    // since 1.2.1 (reporterType for old versions)
-    reporter = "json"
     output = "someFile.json"
 }
 ```
@@ -302,7 +296,7 @@ Diktat can be run via spotless-maven-plugin since version 2.8.0
 ```
 </details>
 
-## GitHub Native Integration
+## GitHub Integration
 We suggest everyone to use common ["sarif"](https://docs.oasis-open.org/sarif/sarif/v2.0/sarif-v2.0.html) format as a `reporter` (`reporterType`)  in CI/CD.
 GitHub has an [integration](https://docs.github.com/en/code-security/code-scanning/integrating-with-code-scanning/sarif-support-for-code-scanning)
 with SARIF format and provides you a native reporting of diktat issues in Pull Requests.
@@ -337,6 +331,18 @@ mvn -B diktat:check@diktat -Ddiktat.githubActions=true
         with:
           sarif_file: ${{ github.workspace }}
 ```
+
+*Note*: `codeql-action/upload-sarif` limits the number of uploaded files at 15. If your project has more than 15 subprojects,
+the limit will be exceeded and the step will fail. To solve this issue one can merge SARIF reports.
+
+`diktat-gradle-plugin` provides this capability with `mergeDiktatReports` task. This task aggregates reports of all diktat tasks
+of all Gradle project, which produce SARIF reports, and outputs the merged report into root project's build directory. Then this single
+file can be used as an input for Github action:
+```yaml
+with:
+    sarif_file: build/reports/diktat/diktat-merged.sarif
+```
+
 </details>
 
 ## <a name="config"></a> Customizations via `diktat-analysis.yml`
diff --git a/diktat-gradle-plugin/build.gradle.kts b/diktat-gradle-plugin/build.gradle.kts
index 95c506dbe5..b5872f5860 100644
--- a/diktat-gradle-plugin/build.gradle.kts
+++ b/diktat-gradle-plugin/build.gradle.kts
@@ -34,6 +34,7 @@ val junitVersion = project.properties.getOrDefault("junitVersion", "5.8.1") as S
 val jacocoVersion = project.properties.getOrDefault("jacocoVersion", "0.8.7") as String
 dependencies {
     implementation(kotlin("gradle-plugin-api"))
+    implementation("io.github.detekt.sarif4k:sarif4k:0.0.1")
 
     implementation("org.cqfn.diktat:diktat-common:$diktatVersion") {
         exclude("org.jetbrains.kotlin", "kotlin-compiler-embeddable")
diff --git a/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatGradlePlugin.kt b/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatGradlePlugin.kt
index e799c81815..f0a0acbc36 100644
--- a/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatGradlePlugin.kt
+++ b/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatGradlePlugin.kt
@@ -1,5 +1,6 @@
 package org.cqfn.diktat.plugin.gradle
 
+import org.cqfn.diktat.plugin.gradle.tasks.configureMergeReportsTask
 import generated.DIKTAT_VERSION
 import generated.KTLINT_VERSION
 import org.gradle.api.Plugin
@@ -26,9 +27,7 @@ class DiktatGradlePlugin : Plugin<Project> {
             diktatConfigFile = project.rootProject.file("diktat-analysis.yml")
         }
 
-        // only gradle 7+ (or maybe 6.8) will embed kotlin 1.4+, kx.serialization is incompatible with kotlin 1.3, so until then we have to use JavaExec wrapper
-        // FixMe: when gradle with kotlin 1.4 is out, proper configurable tasks should be added
-        // configuration to provide JavaExec with correct classpath
+        // Configuration that will be used as classpath for JavaExec task.
         val diktatConfiguration = project.configurations.create(DIKTAT_CONFIGURATION) { configuration ->
             configuration.isVisible = false
             configuration.dependencies.add(project.dependencies.create("com.pinterest:ktlint:$KTLINT_VERSION", closureOf<ExternalModuleDependency> {
@@ -47,6 +46,7 @@ class DiktatGradlePlugin : Plugin<Project> {
 
         project.registerDiktatCheckTask(diktatExtension, diktatConfiguration, patternSet)
         project.registerDiktatFixTask(diktatExtension, diktatConfiguration, patternSet)
+        project.configureMergeReportsTask(diktatExtension)
     }
 
     companion object {
@@ -70,6 +70,11 @@ class DiktatGradlePlugin : Plugin<Project> {
          */
         const val DIKTAT_FIX_TASK = "diktatFix"
 
+        /**
+         * Name of the task that merges SARIF reports of diktat tasks
+         */
+        internal const val MERGE_SARIF_REPORTS_TASK_NAME = "mergeDiktatReports"
+
         /**
          * Version of JVM with more strict module system, which requires `add-opens` for kotlin compiler
          */
diff --git a/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskBase.kt b/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskBase.kt
index a33ede567a..abd9e6fccf 100644
--- a/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskBase.kt
+++ b/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskBase.kt
@@ -27,8 +27,6 @@ import org.gradle.api.tasks.util.PatternSet
 import org.gradle.util.GradleVersion
 
 import java.io.File
-import java.nio.file.Files
-import java.nio.file.Paths
 import javax.inject.Inject
 
 /**
@@ -148,27 +146,21 @@ open class DiktatJavaExecTaskBase @Inject constructor(
     @Suppress("FUNCTION_BOOLEAN_PREFIX")
     override fun getIgnoreFailures(): Boolean = ignoreFailuresProp.getOrElse(false)
 
+    @Suppress("AVOID_NULL_CHECKS")
     private fun reporterFlag(diktatExtension: DiktatExtension): String = buildString {
         val reporterFlag = project.createReporterFlag(diktatExtension)
         append(reporterFlag)
-        val isSarifReporterActive = reporterFlag.contains("sarif")
-        if (isSarifReporterActive) {
+        if (isSarifReporterActive(reporterFlag)) {
             // need to set user.home specially for ktlint, so it will be able to put a relative path URI in SARIF
             systemProperty("user.home", project.rootDir.toString())
         }
 
-        val outFlag = when {
-            // githubActions should have higher priority than a custom input
-            diktatExtension.githubActions -> {
-                val reportDir = Files.createDirectories(Paths.get("${project.buildDir}/reports/diktat"))
-                outputs.dir(reportDir)
-                ",output=${reportDir.resolve("diktat.sarif")}"
-            }
-            diktatExtension.output.isNotEmpty() -> ",output=${diktatExtension.output}"
-            else -> ""
+        val outputFile = project.getOutputFile(diktatExtension)
+        if (outputFile != null) {
+            outputs.file(outputFile)
+            val outFlag = ",output=$outputFile"
+            append(outFlag)
         }
-
-        append(outFlag)
     }
 
     @Suppress("MagicNumber")
diff --git a/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/Utils.kt b/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/Utils.kt
index bc5a7bf1eb..9181043b48 100644
--- a/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/Utils.kt
+++ b/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/Utils.kt
@@ -8,6 +8,9 @@ package org.cqfn.diktat.plugin.gradle
 
 import groovy.lang.Closure
 import org.gradle.api.Project
+import java.io.File
+import java.nio.file.Files
+import java.nio.file.Paths
 
 @Suppress(
     "MISSING_KDOC_TOP_LEVEL",
@@ -38,18 +41,18 @@ fun <T> Any.closureOf(action: T.() -> Unit): Closure<Any?> =
     KotlinClosure1(action, this, this)
 
 /**
- * Create CLI flag to select reporter based on [diktatExtension]
+ * Create CLI flag to set reporter for ktlint based on [diktatExtension].
+ * [DiktatExtension.githubActions] should have higher priority than a custom input.
  *
- * @param diktatExtension project extension of type [DiktatExtension]
- * @return CLI flag
+ * @param diktatExtension extension of type [DiktatExtension]
+ * @return CLI flag as string
  */
-internal fun Project.createReporterFlag(diktatExtension: DiktatExtension): String {
+fun Project.createReporterFlag(diktatExtension: DiktatExtension): String {
     val name = diktatExtension.reporter.trim()
     val validReporters = listOf("sarif", "plain", "json", "html")
     val reporterFlag = when {
         diktatExtension.githubActions -> {
             if (diktatExtension.reporter.isNotEmpty()) {
-                // githubActions should have higher priority than custom input
                 logger.warn("`diktat.githubActions` is set to true, so custom reporter [$name] will be ignored and SARIF reporter will be used")
             }
             "--reporter=sarif"
@@ -67,3 +70,27 @@ internal fun Project.createReporterFlag(diktatExtension: DiktatExtension): Strin
 
     return reporterFlag
 }
+
+/**
+ * Get destination file for Diktat report or null if stdout is used.
+ * [DiktatExtension.githubActions] should have higher priority than a custom input.
+ *
+ * @param diktatExtension extension of type [DiktatExtension]
+ * @return destination [File] or null if stdout is used
+ */
+internal fun Project.getOutputFile(diktatExtension: DiktatExtension): File? = when {
+    diktatExtension.githubActions -> {
+        val reportDir = Files.createDirectories(Paths.get("${project.buildDir}/reports/diktat"))
+        reportDir.resolve("diktat.sarif").toFile()
+    }
+    diktatExtension.output.isNotEmpty() -> file(diktatExtension.output)
+    else -> null
+}
+
+/**
+ * Whether SARIF reporter is enabled or not
+ *
+ * @param reporterFlag
+ * @return whether SARIF reporter is enabled
+ */
+internal fun isSarifReporterActive(reporterFlag: String) = reporterFlag.contains("sarif")
diff --git a/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/tasks/SarifReportMergeTask.kt b/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/tasks/SarifReportMergeTask.kt
new file mode 100644
index 0000000000..a94725749c
--- /dev/null
+++ b/diktat-gradle-plugin/src/main/kotlin/org/cqfn/diktat/plugin/gradle/tasks/SarifReportMergeTask.kt
@@ -0,0 +1,101 @@
+package org.cqfn.diktat.plugin.gradle.tasks
+
+import org.cqfn.diktat.plugin.gradle.DiktatExtension
+import org.cqfn.diktat.plugin.gradle.DiktatGradlePlugin.Companion.MERGE_SARIF_REPORTS_TASK_NAME
+import org.cqfn.diktat.plugin.gradle.DiktatJavaExecTaskBase
+import org.cqfn.diktat.plugin.gradle.createReporterFlag
+import org.cqfn.diktat.plugin.gradle.getOutputFile
+import org.cqfn.diktat.plugin.gradle.isSarifReporterActive
+import io.github.detekt.sarif4k.SarifSchema210
+import org.gradle.api.DefaultTask
+import org.gradle.api.Project
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.tasks.InputFiles
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.PathSensitive
+import org.gradle.api.tasks.PathSensitivity
+import org.gradle.api.tasks.TaskAction
+import org.gradle.api.tasks.TaskExecutionException
+import kotlinx.serialization.SerializationException
+import kotlinx.serialization.decodeFromString
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+
+/**
+ * A task to merge SARIF reports produced by diktat check / diktat fix tasks.
+ */
+abstract class SarifReportMergeTask : DefaultTask() {
+    /**
+     * Source reports that should be merged
+     */
+    @get:InputFiles
+    @get:PathSensitive(PathSensitivity.RELATIVE)
+    abstract val input: ConfigurableFileCollection
+
+    /**
+     * Destination for the merged report
+     */
+    @get:OutputFile
+    abstract val output: RegularFileProperty
+
+    /**
+     * @throws TaskExecutionException if failed to deserialize SARIF
+     */
+    @TaskAction
+    fun mergeReports() {
+        val sarifReports = input.files
+            .filter { it.exists() }
+            .also { logger.info("Merging SARIF reports from files $it") }
+            .map {
+                try {
+                    Json.decodeFromString<SarifSchema210>(it.readText())
+                } catch (e: SerializationException) {
+                    logger.error("Couldn't deserialize JSON: is ${it.canonicalPath} a SARIF file?")
+                    throw TaskExecutionException(this, e)
+                }
+            }
+
+        if (sarifReports.isEmpty()) {
+            logger.warn("Cannot perform merging of SARIF reports because no matching files were found; " +
+                    "Is SARIF reporter active?"
+            )
+            return
+        }
+
+        // All reports should contain identical metadata, so we are using the first one as a base.
+        val templateReport = sarifReports.first()
+        val allResults = sarifReports.flatMap { sarifSchema ->
+            sarifSchema.runs
+                .flatMap { it.results.orEmpty() }
+        }
+        val mergedSarif = templateReport.copy(
+            runs = listOf(templateReport.runs.first().copy(results = allResults))
+        )
+
+        output.get().asFile.writeText(Json.encodeToString(mergedSarif))
+    }
+}
+
+/**
+ * @param diktatExtension extension of type [DiktatExtension]
+ */
+internal fun Project.configureMergeReportsTask(diktatExtension: DiktatExtension) {
+    if (path == rootProject.path) {
+        tasks.register(MERGE_SARIF_REPORTS_TASK_NAME, SarifReportMergeTask::class.java) { reportMergeTask ->
+            val diktatReportsDir = "${project.buildDir}/reports/diktat"
+            val mergedReportFile = project.file("$diktatReportsDir/diktat-merged.sarif")
+            reportMergeTask.outputs.file(mergedReportFile)
+            reportMergeTask.output.set(mergedReportFile)
+        }
+    }
+    val reportMergeTaskTaskProvider = rootProject.tasks.named(MERGE_SARIF_REPORTS_TASK_NAME, SarifReportMergeTask::class.java) { reportMergeTask ->
+        if (isSarifReporterActive(createReporterFlag(diktatExtension))) {
+            getOutputFile(diktatExtension)?.let { reportMergeTask.input.from(it) }
+            reportMergeTask.shouldRunAfter(tasks.withType(DiktatJavaExecTaskBase::class.java))
+        }
+    }
+    tasks.withType(DiktatJavaExecTaskBase::class.java).configureEach { diktatJavaExecTaskBase ->
+        diktatJavaExecTaskBase.finalizedBy(reportMergeTaskTaskProvider)
+    }
+}
diff --git a/diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskTest.kt b/diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskTest.kt
index 07af3cd3b9..a4d79fb08d 100644
--- a/diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskTest.kt
+++ b/diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/DiktatJavaExecTaskTest.kt
@@ -91,7 +91,7 @@ class DiktatJavaExecTaskTest {
     @Test
     fun `check command line has reporter type and output`() {
         assertCommandLineEquals(
-            listOf(null, "--reporter=json,output=some.txt")
+            listOf(null, "--reporter=json,output=${project.projectDir.resolve("some.txt")}")
         ) {
             inputs { exclude("*") }
             diktatConfigFile = project.file("../diktat-analysis.yml")
diff --git a/diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/ReporterSelectionTest.kt b/diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/ReporterSelectionTest.kt
new file mode 100644
index 0000000000..472480f89f
--- /dev/null
+++ b/diktat-gradle-plugin/src/test/kotlin/org/cqfn/diktat/plugin/gradle/ReporterSelectionTest.kt
@@ -0,0 +1,34 @@
+package org.cqfn.diktat.plugin.gradle
+
+import org.gradle.api.Project
+import org.gradle.api.tasks.util.PatternSet
+import org.gradle.testfixtures.ProjectBuilder
+import org.junit.jupiter.api.Assertions
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+class ReporterSelectionTest {
+    private val projectBuilder = ProjectBuilder.builder()
+    private lateinit var project: Project
+
+    @BeforeEach
+    fun setUp() {
+        project = projectBuilder.build()
+        // mock kotlin sources
+        project.mkdir("src/main/kotlin")
+        project.file("src/main/kotlin/Test.kt").createNewFile()
+        project.pluginManager.apply(DiktatGradlePlugin::class.java)
+    }
+
+    @Test
+    fun `should fallback to plain reporter for unknown reporter types`() {
+        val diktatExtension = DiktatExtension(PatternSet()).apply {
+            reporter = "jsonx"
+        }
+
+        Assertions.assertEquals(
+            "--reporter=plain",
+            project.createReporterFlag(diktatExtension)
+        )
+    }
+}