diff --git a/services/form/app/services/__init__.py b/services/form/app/services/__init__.py
index 7af21b5..714cb35 100644
--- a/services/form/app/services/__init__.py
+++ b/services/form/app/services/__init__.py
@@ -1 +1,5 @@
 """Business logic layer."""
+
+from app.services.submission_service import SubmissionService
+
+__all__ = ["SubmissionService"]
diff --git a/services/form/app/services/submission_service.py b/services/form/app/services/submission_service.py
new file mode 100644
index 0000000..b675f85
--- /dev/null
+++ b/services/form/app/services/submission_service.py
@@ -0,0 +1,247 @@
+"""Submission service layer for managing form submissions."""
+
+from datetime import datetime, timezone
+
+from bson import ObjectId
+from motor.motor_asyncio import AsyncIOMotorDatabase
+from pymongo.errors import PyMongoError
+
+from app.models.common import PyObjectId
+from app.models.form import FormInDB
+from app.models.submission import SubmissionCreate, SubmissionInDB
+from app.utils.logger import logger
+
+
+class SubmissionService:
+    """
+    Service layer for Submission operations.
+    Handles business logic and database interactions for submissions.
+    """
+
+    def __init__(self, db: AsyncIOMotorDatabase):
+        self.db = db
+        self.collection = db["submissions"]
+        self.forms_collection = db["forms"]
+
+    def _to_object_id(self, obj_id: PyObjectId) -> ObjectId:
+        """
+        Convert PyObjectId to ObjectId for MongoDB queries.
+
+        Args:
+            obj_id: PyObjectId (which is Annotated[ObjectId, ...])
+
+        Returns:
+            ObjectId for MongoDB operations
+
+        Raises:
+            ValueError: If invalid ObjectId string is provided
+        """
+        if isinstance(obj_id, ObjectId):
+            return obj_id
+        if isinstance(obj_id, str):
+            if not ObjectId.is_valid(obj_id):
+                raise ValueError(f"Invalid ObjectId: {obj_id}")
+            return ObjectId(obj_id)
+        return obj_id
+
+    def _document_to_submission(self, doc: dict | None) -> SubmissionInDB | None:
+        """
+        Convert MongoDB document to SubmissionInDB model.
+
+        Args:
+            doc: MongoDB document dict or None
+
+        Returns:
+            SubmissionInDB instance or None
+        """
+        if doc is None:
+            return None
+
+        try:
+            return SubmissionInDB.model_validate(doc)
+        except Exception as e:
+            logger.error(f"Error converting document to SubmissionInDB: {e}")
+            raise
+
+    async def _validate_form(self, form_id: PyObjectId) -> FormInDB:
+        """
+        Validate form exists, is active, and within date range.
+
+        Args:
+            form_id: Form ID to validate
+
+        Returns:
+            FormInDB instance if valid
+
+        Raises:
+            ValueError: If form not found, inactive, not started yet, or deadline passed
+        """
+        object_id = self._to_object_id(form_id)
+
+        try:
+            form_doc = await self.forms_collection.find_one({"_id": object_id})
+        except PyMongoError as e:
+            logger.error(f"Database error while validating form {form_id}: {e}")
+            raise
+
+        if form_doc is None:
+            raise ValueError(f"Form not found with id: {form_id}")
+
+        try:
+            form = FormInDB.model_validate(form_doc)
+        except Exception as e:
+            logger.error(f"Error converting form document to FormInDB: {e}")
+            raise ValueError(f"Invalid form data for id: {form_id}")
+
+        if not form.is_active:
+            raise ValueError("Form is not active")
+
+        now = datetime.now(timezone.utc)
+
+        # Handle timezone-naive datetimes from MongoDB
+        if form.start_date is not None:
+            start_date = form.start_date
+            if start_date.tzinfo is None:
+                start_date = start_date.replace(tzinfo=timezone.utc)
+            if start_date > now:
+                raise ValueError("Form has not started yet")
+
+        if form.deadline is not None:
+            deadline = form.deadline
+            if deadline.tzinfo is None:
+                deadline = deadline.replace(tzinfo=timezone.utc)
+            if deadline < now:
+                raise ValueError("Form deadline has passed")
+
+        return form
+
+    async def create_submission(
+        self, submission_data: SubmissionCreate
+    ) -> SubmissionInDB:
+        """
+        Create a new submission.
+
+        Args:
+            submission_data: Submission data to create
+
+        Returns:
+            Created SubmissionInDB instance
+
+        Raises:
+            ValueError: For validation errors (form not found, inactive, not started, deadline passed)
+            PyMongoError: For database errors
+        """
+        logger.info(f"Creating submission for form {submission_data.form_id}")
+
+        # Validate form
+        await self._validate_form(submission_data.form_id)
+
+        # Prepare submission document
+        submission_doc = submission_data.model_dump(by_alias=True, exclude={"id"})
+        submission_doc["_id"] = ObjectId()
+        submission_doc["submitted_at"] = datetime.now(timezone.utc)
+        # Ensure form_id is stored as ObjectId, not string
+        submission_doc["form_id"] = self._to_object_id(submission_data.form_id)
+
+        object_id = self._to_object_id(submission_data.form_id)
+
+        try:
+            # Insert submission
+            await self.collection.insert_one(submission_doc)
+
+            # Atomically increment form's submission_count
+            await self.forms_collection.update_one(
+                {"_id": object_id}, {"$inc": {"submission_count": 1}}
+            )
+
+            logger.info(
+                f"Successfully created submission {submission_doc['_id']} "
+                f"for form {submission_data.form_id}"
+            )
+
+            return self._document_to_submission(submission_doc)
+
+        except PyMongoError as e:
+            logger.error(f"Database error while creating submission: {e}")
+            raise
+
+    async def get_submission_by_id(
+        self, submission_id: PyObjectId
+    ) -> SubmissionInDB | None:
+        """
+        Get submission by ID.
+
+        Args:
+            submission_id: Submission ID
+
+        Returns:
+            SubmissionInDB instance if found, None otherwise
+
+        Raises:
+            PyMongoError: For database errors
+        """
+        object_id = self._to_object_id(submission_id)
+
+        try:
+            doc = await self.collection.find_one({"_id": object_id})
+            return self._document_to_submission(doc)
+        except PyMongoError as e:
+            logger.error(
+                f"Database error while getting submission {submission_id}: {e}"
+            )
+            raise
+
+    async def get_submissions_by_form_id(
+        self, form_id: PyObjectId, skip: int = 0, limit: int = 10
+    ) -> tuple[list[SubmissionInDB], int]:
+        """
+        Get submissions by form ID with pagination.
+
+        Args:
+            form_id: Form ID
+            skip: Number of documents to skip (default: 0)
+            limit: Maximum number of documents to return (default: 10, max: 100)
+
+        Returns:
+            Tuple of (list of SubmissionInDB, total count)
+
+        Raises:
+            ValueError: For invalid pagination parameters
+            PyMongoError: For database errors
+        """
+        # Validate pagination parameters
+        if skip < 0:
+            raise ValueError("skip must be >= 0")
+        if limit < 1 or limit > 100:
+            raise ValueError("limit must be between 1 and 100")
+
+        object_id = self._to_object_id(form_id)
+
+        try:
+            # Count total submissions
+            total_count = await self.collection.count_documents({"form_id": object_id})
+
+            # Query with pagination
+            cursor = (
+                self.collection.find({"form_id": object_id})
+                .sort("submitted_at", -1)
+                .skip(skip)
+                .limit(limit)
+            )
+
+            docs = await cursor.to_list(length=limit)
+
+            submissions = []
+            for doc in docs:
+                if doc is not None:
+                    submission = self._document_to_submission(doc)
+                    if submission is not None:
+                        submissions.append(submission)
+
+            return submissions, total_count
+
+        except PyMongoError as e:
+            logger.error(
+                f"Database error while getting submissions for form {form_id}: {e}"
+            )
+            raise