diff --git a/foliary/src/commonMain/composeResources/values/strings.xml b/foliary/src/commonMain/composeResources/values/strings.xml
index 4af99b5..66b2c17 100644
--- a/foliary/src/commonMain/composeResources/values/strings.xml
+++ b/foliary/src/commonMain/composeResources/values/strings.xml
@@ -70,6 +70,8 @@
     <string name="today_celebration_button">Create a new task</string>
     <string name="today_completed_header">Completed today (%1$d)</string>
     <string name="today_completed_header_a11y">Toggle completed tasks</string>
+    <string name="today_undo_snackbar_message">Task marked as done</string>
+    <string name="today_undo_snackbar_action">Undo</string>
     <!-- endregion -->
 
     <!-- region Create Task -->
diff --git a/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/today/TodayScreen.kt b/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/today/TodayScreen.kt
index 6145d04..72117a2 100644
--- a/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/today/TodayScreen.kt
+++ b/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/today/TodayScreen.kt
@@ -23,8 +23,13 @@ import androidx.compose.foundation.lazy.items
 import androidx.compose.material3.HorizontalDivider
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.SnackbarDuration
+import androidx.compose.material3.SnackbarHost
+import androidx.compose.material3.SnackbarHostState
+import androidx.compose.material3.SnackbarResult
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
@@ -37,7 +42,6 @@ import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.unit.dp
 import com.composables.icons.lucide.ChevronDown
 import com.composables.icons.lucide.Lucide
-import dev.appoutlet.foliary.core.navigation.Navigator
 import dev.appoutlet.foliary.core.ui.component.button.FoliaryAddButton
 import dev.appoutlet.foliary.core.ui.component.button.FoliarySecondaryButton
 import dev.appoutlet.foliary.core.ui.component.layout.FoliaryEmptyContent
@@ -64,7 +68,10 @@ import foliary.foliary.generated.resources.today_empty_button
 import foliary.foliary.generated.resources.today_empty_description
 import foliary.foliary.generated.resources.today_empty_title
 import foliary.foliary.generated.resources.today_title
+import foliary.foliary.generated.resources.today_undo_snackbar_action
+import foliary.foliary.generated.resources.today_undo_snackbar_message
 import foliary.foliary.generated.resources.today_welcome
+import kotlinx.coroutines.channels.Channel
 import org.jetbrains.compose.resources.painterResource
 import org.jetbrains.compose.resources.stringResource
 import org.koin.compose.viewmodel.koinViewModel
@@ -72,22 +79,73 @@ import org.koin.compose.viewmodel.koinViewModel
 @Composable
 fun TodayScreen(lazyListState: LazyListState) {
     val viewModel = koinViewModel<TodayViewModel>()
+    val snackbarHostState = remember { SnackbarHostState() }
+    val undoChannel = remember { Channel<TodayAction.ShowUndoSnackbar>(Channel.CONFLATED) }
 
-    Screen(
-        screenName = "TodayScreen",
-        viewModelProvider = { viewModel },
-        onAction = ::onAction
-    ) { viewData ->
-        when (viewData) {
-            TodayViewData.Idle -> {}
-            TodayViewData.Loading -> LoadingIndicator()
-            is TodayViewData.Loaded,
-            is TodayViewData.Empty,
-            is TodayViewData.Celebration -> TodayScreenContent(
-                lazyListState = lazyListState,
-                viewData = viewData,
-                onEvent = viewModel::onEvent,
+    TodayUndoSnackbar(
+        events = undoChannel,
+        hostState = snackbarHostState,
+        message = stringResource(Res.string.today_undo_snackbar_message),
+        actionLabel = stringResource(Res.string.today_undo_snackbar_action),
+        onUndo = { taskId -> viewModel.onEvent(TodayEvent.MarkTaskAsNotCompleted(taskId)) }
+    )
+
+    Box(modifier = Modifier.fillMaxSize()) {
+        Screen(
+            screenName = "TodayScreen",
+            viewModelProvider = { viewModel },
+            onAction = { action, navigator ->
+                when (action) {
+                    TodayAction.NavigateToCreateTask -> navigator.navigate(CreateTaskNavKey())
+                    TodayAction.NavigateToSignIn -> navigator.setRoot(SignInNavKey)
+                    is TodayAction.NavigateToTaskDetail -> navigator.navigate(TaskDetailNavKey(action.taskId))
+                    is TodayAction.ShowUndoSnackbar -> undoChannel.trySend(action)
+                }
+            }
+        ) { viewData ->
+            when (viewData) {
+                TodayViewData.Idle -> {}
+                TodayViewData.Loading -> LoadingIndicator()
+                is TodayViewData.Loaded,
+                is TodayViewData.Empty,
+                is TodayViewData.Celebration -> TodayScreenContent(
+                    lazyListState = lazyListState,
+                    viewData = viewData,
+                    onEvent = viewModel::onEvent,
+                )
+            }
+        }
+
+        SnackbarHost(
+            hostState = snackbarHostState,
+            modifier = Modifier
+                .align(Alignment.BottomCenter)
+                .windowInsetsPadding(WindowInsets.safeDrawing.only(WindowInsetsSides.Horizontal))
+                .padding(horizontal = 16.dp)
+        )
+    }
+}
+
+@Composable
+internal fun TodayUndoSnackbar(
+    events: Channel<TodayAction.ShowUndoSnackbar>,
+    hostState: SnackbarHostState,
+    message: String,
+    actionLabel: String,
+    onUndo: (String) -> Unit,
+    duration: SnackbarDuration = SnackbarDuration.Long,
+) {
+    LaunchedEffect(events) {
+        for (event in events) {
+            hostState.currentSnackbarData?.dismiss()
+            val result = hostState.showSnackbar(
+                message = message,
+                actionLabel = actionLabel,
+                duration = duration,
             )
+            if (result == SnackbarResult.ActionPerformed) {
+                onUndo(event.taskId)
+            }
         }
     }
 }
@@ -317,13 +375,5 @@ private fun TodayScreenCelebrationContent(
     }
 }
 
-private fun onAction(action: TodayAction, navigator: Navigator) {
-    when (action) {
-        TodayAction.NavigateToCreateTask -> navigator.navigate(CreateTaskNavKey())
-        TodayAction.NavigateToSignIn -> navigator.setRoot(SignInNavKey)
-        is TodayAction.NavigateToTaskDetail -> navigator.navigate(TaskDetailNavKey(action.taskId))
-    }
-}
-
 private const val RotationCollapsed = -90f
 private const val RotationExpanded = 0f
diff --git a/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/today/TodayViewModel.kt b/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/today/TodayViewModel.kt
index b7c92c1..616ef08 100644
--- a/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/today/TodayViewModel.kt
+++ b/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/today/TodayViewModel.kt
@@ -99,6 +99,7 @@ class TodayViewModel(
     private fun onMarkTaskAsCompleted(taskId: String) = intent {
         celebrationPending = true
         taskRepository.markCompleted(Uuid.parse(taskId))
+        postSideEffect(TodayAction.ShowUndoSnackbar(taskId))
     }
 
     private fun onMarkTaskAsNotCompleted(taskId: String) = intent {
@@ -142,6 +143,7 @@ sealed interface TodayAction : Action {
     data object NavigateToCreateTask : TodayAction
     data object NavigateToSignIn : TodayAction
     data class NavigateToTaskDetail(val taskId: String) : TodayAction
+    data class ShowUndoSnackbar(val taskId: String) : TodayAction
 }
 
 sealed interface TodayEvent {
diff --git a/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingScreen.kt b/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingScreen.kt
index efb48f0..d8cc95d 100644
--- a/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingScreen.kt
+++ b/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingScreen.kt
@@ -235,7 +235,11 @@ private fun UpcomingTaskItem(
                 .padding(horizontal = 16.dp, vertical = 4.dp)
                 .align(Alignment.Center),
             task = task,
-            onCompletedChange = {},
+            onCompletedChange = { isCompleted ->
+                if (isCompleted) {
+                    onEvent(UpcomingEvent.MarkTaskAsCompleted(task.id))
+                }
+            },
             onClick = { onEvent(UpcomingEvent.OnTaskClick(task.id)) },
             onPillClick = { clickedPill ->
                 when (clickedPill) {
diff --git a/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingViewModel.kt b/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingViewModel.kt
index 204a3d0..a42af86 100644
--- a/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingViewModel.kt
+++ b/foliary/src/commonMain/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingViewModel.kt
@@ -29,9 +29,14 @@ class UpcomingViewModel(
             UpcomingEvent.OnAddTaskClick -> onAddTaskClick()
             is UpcomingEvent.OnTaskClick -> onTaskClick(event.taskId)
             is UpcomingEvent.OnUrlPillClick -> onUrlPillClick(event.taskId)
+            is UpcomingEvent.MarkTaskAsCompleted -> onMarkTaskAsCompleted(event.taskId)
         }
     }
 
+    private fun onMarkTaskAsCompleted(taskId: String) = intent {
+        taskRepository.markCompleted(Uuid.parse(taskId))
+    }
+
     private fun onAddTaskClick() = intent {
         postSideEffect(UpcomingAction.NavigateToCreateTask)
     }
@@ -72,6 +77,7 @@ sealed interface UpcomingEvent {
     data object OnAddTaskClick : UpcomingEvent
     data class OnTaskClick(val taskId: String) : UpcomingEvent
     data class OnUrlPillClick(val taskId: String) : UpcomingEvent
+    data class MarkTaskAsCompleted(val taskId: String) : UpcomingEvent
 }
 
 sealed interface UpcomingAction : Action {
diff --git a/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/today/TodayScreenTest.kt b/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/today/TodayScreenTest.kt
index e72d685..45f91e5 100644
--- a/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/today/TodayScreenTest.kt
+++ b/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/today/TodayScreenTest.kt
@@ -1,6 +1,10 @@
 package dev.appoutlet.foliary.feature.today
 
 import androidx.compose.foundation.lazy.rememberLazyListState
+import androidx.compose.material3.SnackbarDuration
+import androidx.compose.material3.SnackbarHost
+import androidx.compose.material3.SnackbarHostState
+import androidx.compose.runtime.remember
 import androidx.compose.ui.test.ExperimentalTestApi
 import androidx.compose.ui.test.assertIsDisplayed
 import androidx.compose.ui.test.onNodeWithContentDescription
@@ -22,6 +26,7 @@ import foliary.foliary.generated.resources.today_empty_title
 import foliary.foliary.generated.resources.today_title
 import foliary.foliary.generated.resources.today_welcome
 import io.kotest.matchers.shouldBe
+import kotlinx.coroutines.channels.Channel
 import org.jetbrains.compose.resources.getString
 import kotlin.test.Test
 
@@ -316,4 +321,35 @@ class TodayScreenTest {
 
         event shouldBe TodayEvent.OnUrlPillClick(task.id)
     }
+
+    @Test
+    fun `should display undo snackbar and invoke onUndo when action is tapped`() = runComposeUiTest {
+        val channel = Channel<TodayAction.ShowUndoSnackbar>(Channel.CONFLATED)
+        var undoneTaskId: String? = null
+
+        setContent {
+            val hostState = remember { SnackbarHostState() }
+
+            TodayUndoSnackbar(
+                events = channel,
+                hostState = hostState,
+                message = "Task marked as done",
+                actionLabel = "Undo",
+                onUndo = { undoneTaskId = it },
+                duration = SnackbarDuration.Indefinite,
+            )
+
+            SnackbarHost(hostState = hostState)
+        }
+
+        channel.trySend(TodayAction.ShowUndoSnackbar("task-123"))
+        mainClock.advanceTimeBy(1000)
+        waitForIdle()
+
+        onNodeWithText("Task marked as done").assertIsDisplayed()
+        onNodeWithText("Undo").assertIsDisplayed().performClick()
+        waitForIdle()
+
+        undoneTaskId shouldBe "task-123"
+    }
 }
diff --git a/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/today/TodayViewModelTest.kt b/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/today/TodayViewModelTest.kt
index c06e843..a36b7aa 100644
--- a/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/today/TodayViewModelTest.kt
+++ b/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/today/TodayViewModelTest.kt
@@ -144,6 +144,7 @@ class TodayViewModelTest : ViewModelTest<TodayViewModel, TodayViewData, TodayAct
             )
 
             viewModel.onEvent(TodayEvent.MarkTaskAsCompleted(pendingTask.id.toString()))
+            expectSideEffect(TodayAction.ShowUndoSnackbar(pendingTask.id.toString()))
             delay(1.milliseconds)
             tasksFlow.value = listOf(completedTask)
 
@@ -189,6 +190,7 @@ class TodayViewModelTest : ViewModelTest<TodayViewModel, TodayViewData, TodayAct
             )
 
             viewModel.onEvent(TodayEvent.MarkTaskAsCompleted(pendingTask.id.toString()))
+            expectSideEffect(TodayAction.ShowUndoSnackbar(pendingTask.id.toString()))
             delay(1.milliseconds)
             tasksFlow.value = listOf(completedTask)
 
@@ -257,7 +259,7 @@ class TodayViewModelTest : ViewModelTest<TodayViewModel, TodayViewData, TodayAct
     }
 
     @Test
-    fun `should call markCompleted when MarkTaskAsCompleted is emitted`() {
+    fun `should call markCompleted and emit ShowUndoSnackbar side effect when MarkTaskAsCompleted is emitted`() {
         val taskId = Uuid.parse("550e8400-e29b-41d4-a716-446655440000")
 
         every { mockAuthenticationRepository.currentUser() } returns UserInfo.fixture()
@@ -269,14 +271,15 @@ class TodayViewModelTest : ViewModelTest<TodayViewModel, TodayViewData, TodayAct
             expectState(TodayViewData.Empty(userName = "Messias", completedTasks = emptyList()))
 
             viewModel.onEvent(TodayEvent.MarkTaskAsCompleted(taskId.toString()))
-            delay(1.milliseconds)
+
+            expectSideEffect(TodayAction.ShowUndoSnackbar(taskId.toString()))
         }
 
         verifySuspend { mockTaskRepository.markCompleted(taskId) }
     }
 
     @Test
-    fun `should call markNotCompleted when MarkTaskAsNotCompleted is emitted`() {
+    fun `should call markNotCompleted without emitting ShowUndoSnackbar when MarkTaskAsNotCompleted is emitted`() {
         val taskId = Uuid.parse("550e8400-e29b-41d4-a716-446655440000")
 
         every { mockAuthenticationRepository.currentUser() } returns UserInfo.fixture()
diff --git a/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingScreenTest.kt b/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingScreenTest.kt
index 8fd377a..b2c0864 100644
--- a/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingScreenTest.kt
+++ b/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingScreenTest.kt
@@ -149,4 +149,28 @@ class UpcomingScreenTest {
 
         event shouldBe UpcomingEvent.OnUrlPillClick(task.id)
     }
+
+    @Test
+    fun `should emit MarkTaskAsCompleted event when task card checkbox is clicked`() = runComposeUiTest {
+        var event: UpcomingEvent? = null
+        val task = FoliaryTaskCardViewData.fixture(id = "task-complete-id", isCompleted = false)
+        val group = UpcomingViewData.TaskGroup.fixture(
+            label = UpcomingViewData.GroupLabel.Today,
+            tasks = listOf(task)
+        )
+
+        setContent {
+            UpcomingScreenContent(
+                lazyListState = rememberLazyListState(),
+                viewData = UpcomingViewData.Loaded(listOf(group)),
+                onEvent = { event = it },
+            )
+        }
+
+        onNodeWithTag("FoliaryTaskCard:Checkbox", useUnmergedTree = true)
+            .assertIsDisplayed()
+            .performClick()
+
+        event shouldBe UpcomingEvent.MarkTaskAsCompleted("task-complete-id")
+    }
 }
diff --git a/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingViewModelTest.kt b/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingViewModelTest.kt
index 51caea5..d1b6e32 100644
--- a/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingViewModelTest.kt
+++ b/foliary/src/commonTest/kotlin/dev/appoutlet/foliary/feature/upcoming/UpcomingViewModelTest.kt
@@ -13,10 +13,13 @@ import dev.mokkery.every
 import dev.mokkery.everySuspend
 import dev.mokkery.mock
 import dev.mokkery.verify
+import dev.mokkery.verifySuspend
 import io.kotest.matchers.shouldBe
 import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.flowOf
 import kotlin.test.Test
+import kotlin.time.Duration.Companion.milliseconds
 import kotlin.uuid.Uuid
 
 class UpcomingViewModelTest : ViewModelTest<UpcomingViewModel, UpcomingViewData, UpcomingAction>() {
@@ -112,6 +115,33 @@ class UpcomingViewModelTest : ViewModelTest<UpcomingViewModel, UpcomingViewData,
         }
     }
 
+    @Test
+    fun `should call markCompleted when MarkTaskAsCompleted is emitted and update state when pending flow re-emits`() {
+        val taskId = Uuid.parse("550e8400-e29b-41d4-a716-446655440000")
+        val task = Task.fixture(id = taskId)
+        val tasksFlow = MutableStateFlow(listOf(task))
+        val loadedViewData = UpcomingViewData.Loaded(listOf(UpcomingViewData.TaskGroup.fixture()))
+
+        fakeUpcomingViewDataMapper.result = loadedViewData
+        every { mockTaskRepository.findAllPendingTasks() } returns tasksFlow
+        everySuspend { mockTaskRepository.markCompleted(taskId) } returns Unit
+
+        test {
+            expectState(UpcomingViewData.Loading)
+            expectState(loadedViewData)
+
+            fakeUpcomingViewDataMapper.result = UpcomingViewData.Empty
+
+            viewModel.onEvent(UpcomingEvent.MarkTaskAsCompleted(taskId.toString()))
+            delay(1.milliseconds)
+            tasksFlow.value = emptyList()
+
+            expectState(UpcomingViewData.Empty)
+        }
+
+        verifySuspend { mockTaskRepository.markCompleted(taskId) }
+    }
+
     private class FakeUpcomingViewDataMapper(
         timeProvider: DefaultTimeProvider = DefaultTimeProvider(),
     ) : UpcomingViewDataMapper(