diff --git a/src/bin/main.rs b/src/bin/main.rs
index 0ba3ae3..f3ae829 100644
--- a/src/bin/main.rs
+++ b/src/bin/main.rs
@@ -14,6 +14,7 @@ use crate::webserver::start_webserver;
 
 mod init;
 mod webserver;
+mod store;
 
 #[esp_hal_embassy::main]
 async fn main(mut spawner: Spawner) {
diff --git a/src/bin/store/id_mapping.rs b/src/bin/store/id_mapping.rs
new file mode 100644
index 0000000..de25995
--- /dev/null
+++ b/src/bin/store/id_mapping.rs
@@ -0,0 +1,31 @@
+extern crate alloc;
+
+use super::TallyID;
+use alloc::collections::BTreeMap;
+use alloc::string::String;
+
+pub struct Name {
+    pub first: String,
+    pub last: String,
+}
+
+pub struct IDMapping {
+    id_map: BTreeMap<TallyID, Name>,
+}
+
+impl IDMapping {
+    pub fn new() -> Self {
+        IDMapping {
+            id_map: BTreeMap::new(),
+        }
+    }
+
+    pub fn map(&self, id: &TallyID) -> Option<&Name> {
+        self.id_map.get(id)
+    }
+
+    pub fn add_mapping(&mut self, id: TallyID, name: Name) {
+        self.id_map.insert(id, name);
+    }
+}
+
diff --git a/src/bin/store/id_store.rs b/src/bin/store/id_store.rs
new file mode 100644
index 0000000..bc82b35
--- /dev/null
+++ b/src/bin/store/id_store.rs
@@ -0,0 +1,71 @@
+extern crate alloc;
+
+use super::Date;
+use super::IDMapping;
+use super::TallyID;
+use alloc::collections::BTreeMap;
+use alloc::vec::Vec;
+
+pub struct AttendanceDay {
+    date: Date,
+    ids: Vec<TallyID>,
+}
+
+impl AttendanceDay {
+    fn new(date: Date) -> Self {
+        Self {
+            date,
+            ids: Vec::new(),
+        }
+    }
+
+    // Add an ID to the day.
+    // Returns false if ID was already present
+    fn add_id(&mut self, id: TallyID) -> bool {
+        if self.ids.contains(&id) {
+            return false;
+        }
+        self.ids.push(id);
+        true
+    }
+}
+
+pub struct IDStore {
+    days: BTreeMap<Date, AttendanceDay>,
+    mapping: IDMapping,
+}
+
+impl IDStore {
+    pub fn new() -> Self {
+        IDStore {
+            days: BTreeMap::new(),
+            mapping: IDMapping::new(),
+        }
+    }
+
+    pub fn new_from_storage() -> Self {
+        // TODO: implement
+        todo!()
+    }
+
+    /// Add a new id for the current day
+    /// Returns false if ID is already present at the current day.
+    pub fn add_id(&mut self, id: TallyID) -> bool {
+        self.get_current_day().add_id(id)
+    }
+
+    /// Get the `AttendanceDay` of the current day
+    /// Creates a new if not exists
+    pub fn get_current_day(&mut self) -> &mut AttendanceDay {
+        let current_day: Date = 1;
+
+        if self.days.contains_key(&current_day) {
+            return self.days.get_mut(&current_day).unwrap();
+        }
+
+        self.days
+            .insert(current_day, AttendanceDay::new(current_day));
+
+        self.days.get_mut(&current_day.clone()).unwrap()
+    }
+}
diff --git a/src/bin/store/mod.rs b/src/bin/store/mod.rs
new file mode 100644
index 0000000..d72bfee
--- /dev/null
+++ b/src/bin/store/mod.rs
@@ -0,0 +1,8 @@
+mod id_mapping;
+mod id_store;
+
+pub use id_mapping::{IDMapping, Name};
+pub use id_store::IDStore;
+
+pub type TallyID = [u8; 8];
+pub type Date = u64;