diff --git a/.gitignore b/.gitignore
index 24efaf9..7a06208 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 node_modules
 frontend/dist
 build
+bills.db
diff --git a/app.go b/app.go
index a29c6af..4b43295 100644
--- a/app.go
+++ b/app.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"time"
 )
 
 // App struct
@@ -19,3 +20,40 @@ func NewApp() *App {
 func (a *App) startup(ctx context.Context) {
 	a.ctx = ctx
 }
+
+func (a *App) GetBills() WailsBills {
+	res := WailsBills{}
+	bills, err := service.GetAllBills()
+	if err != nil {
+		res.Success = false
+		res.Error = err.Error()
+		return res
+	}
+	res.Success = true
+	res.Data = bills
+	return res
+}
+func (a *App) GetPaymentsForMonth(month time.Time) WailsPayments {
+	res := WailsPayments{}
+	payments, err := service.GetPaymentsForDate(month)
+	if err != nil {
+		res.Success = false
+		res.Error = err.Error()
+		return res
+	}
+	res.Success = true
+	res.Data = payments
+	return res
+}
+func (a *App) SetPaid(billid int64, month time.Time) WailsPayment {
+	res := WailsPayment{}
+	payment, err := service.MarkPaid(billid, month, time.Now())
+	if err!= nil {
+		res.Success = false
+		res.Error = err.Error()
+		return res
+	}
+	res.Success = true
+	res.Data = payment
+	return res
+}
\ No newline at end of file
diff --git a/db.go b/db.go
new file mode 100644
index 0000000..cc74f08
--- /dev/null
+++ b/db.go
@@ -0,0 +1,134 @@
+package main
+
+import (
+	"database/sql"
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+type DB struct {
+	Ready     bool
+	path      string
+	readConn  *sql.DB
+	writeConn *sql.DB
+}
+
+func (db *DB) Open() error {
+	if db.path == "" {
+		return fmt.Errorf("database path not set")
+	}
+
+	file, err := os.Open(db.path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			log.Printf("Database file does not exist at %s, creating", db.path)
+			file, err := os.Create(db.path)
+			if err != nil {
+				return fmt.Errorf("failed to create database file: %v", err)
+			}
+			log.Printf("Database created at %s", db.path)
+			file.Close()
+		} else {
+			return fmt.Errorf("failed to open database file: %v", err)
+		}
+	}
+	file.Close()
+
+	writeConn, err := sql.Open("sqlite3", db.path+"?_journal=WAL&_synchronous=NORMAL")
+	if err != nil {
+		Error.Printf("%++v", err)
+		return err
+	}
+	writeConn.SetMaxOpenConns(1)
+	writeConn.SetConnMaxIdleTime(30 * time.Second)
+	writeConn.SetConnMaxLifetime(30 * time.Second)
+	db.writeConn = writeConn
+
+	readConn, err := sql.Open("sqlite3", db.path+"?mode=ro&_journal=WAL&_synchronous=NORMAL&_mode=ro")
+	if err != nil {
+		Error.Printf("%++v", err)
+		return err
+	}
+	readConn.SetMaxOpenConns(4)
+	readConn.SetConnMaxIdleTime(30 * time.Second)
+	readConn.SetConnMaxLifetime(30 * time.Second)
+	db.readConn = readConn
+
+	db.Ready = true
+	return nil
+}
+
+func (db *DB) Init(ddl string) error {
+	if !db.Ready {
+		return fmt.Errorf("database not ready")
+	}
+
+	var rows map[string]struct{} = make(map[string]struct{})
+	// TODO: Maybe make this better one day...
+	var expected = map[string]struct{}{
+		"Bill":     {},
+		"Payment":   {},
+	}
+
+	res, err := db.readConn.Query("SELECT name FROM sqlite_master WHERE type='table';")
+	if err != nil {
+		Error.Printf("%++v", err)
+		return err
+	}
+	defer res.Close()
+	for res.Next() {
+		var name string
+		err := res.Scan(&name)
+		if err != nil {
+			Error.Printf("%++v", err)
+			return err
+		}
+		rows[name] = struct{}{}
+	}
+
+	var needsInit bool
+	for table := range expected {
+		if _, ok := rows[table]; !ok {
+			log.Printf("Table %s not found, initializing", table)
+			needsInit = true
+			break
+		}
+	}
+
+	if !needsInit {
+		log.Printf("Database already initialized")
+		return nil
+	}
+
+	_, err = db.writeConn.Exec(ddl)
+	if err != nil {
+		Error.Printf("%++v", err)
+		log.Printf("%#v", "Rolling back")
+		_, err2 := db.writeConn.Exec("ROLLBACK;")
+		if err2 != nil {
+			Error.Printf("Error rolling back! %++v", err)
+		}
+		return err
+	}
+
+	log.Printf("Database init OK")
+	return nil
+}
+
+func (db *DB) Close() error {
+	err := db.writeConn.Close()
+	if err != nil {
+		return err
+	}
+
+	err = db.readConn.Close()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
\ No newline at end of file
diff --git a/ddl.sql b/ddl.sql
new file mode 100644
index 0000000..465f587
--- /dev/null
+++ b/ddl.sql
@@ -0,0 +1,19 @@
+begin transaction;
+
+create table Bill (
+	id integer PRIMARY KEY AUTOINCREMENT,
+	name TEXT not null
+);
+create index Bill_name on Bill (name);
+
+create table Payment (
+	id integer PRIMARY KEY AUTOINCREMENT,
+	billid integer,
+	monthFor date not null,
+	paymentDate date
+);
+create unique index Payment_billid_monthFor_unique on Payment (billid, monthFor);
+create index Payment_billid on Payment (billid);
+create index Payment_monthFor on Payment (monthFor);
+
+commit;
\ No newline at end of file
diff --git a/main.go b/main.go
index f672882..fc460da 100644
--- a/main.go
+++ b/main.go
@@ -2,22 +2,66 @@ package main
 
 import (
 	"embed"
+	"fmt"
+	"io"
+	"log"
+	"os"
 
 	"github.com/wailsapp/wails/v2"
 	"github.com/wailsapp/wails/v2/pkg/options"
 	"github.com/wailsapp/wails/v2/pkg/options/assetserver"
 )
 
+var Error *log.Logger
+var Warning *log.Logger
+
+func init() {
+	log.SetFlags(log.Lmicroseconds | log.Lshortfile)
+	logFile, err := os.Create("main.log")
+	if err != nil {
+		log.Printf("Error creating log file: %v", err)
+		os.Exit(1)
+	}
+	logger := io.MultiWriter(os.Stdout, logFile)
+	log.SetOutput(logger)
+
+	Error = log.New(io.MultiWriter(logFile, os.Stderr, os.Stdout),
+		fmt.Sprintf("%sERROR:%s ", "\033[0;101m", "\033[0m"),
+		log.Lmicroseconds|log.Lshortfile)
+	Warning = log.New(io.MultiWriter(logFile, os.Stdout),
+		fmt.Sprintf("%sWarning:%s ", "\033[0;93m", "\033[0m"),
+		log.Lmicroseconds|log.Lshortfile)
+}
+
 //go:embed all:frontend/dist
 var assets embed.FS
 
+//go:embed ddl.sql
+var ddl string
+var service *BillService
+
 func main() {
+	db := DB{
+		path: "bills.db",
+	}
+	db.Open()
+	defer db.Close()
+	err := db.Init(ddl)
+	if err != nil {
+		Error.Printf("Error initializing database: %v", err)
+		return
+	}
+
+	service = &BillService{
+		db: &db,
+	}
+
 	// Create an instance of the app structure
 	app := NewApp()
 
 	// Create application with options
-	err := wails.Run(&options.App{
-		Title:  "wails-template",
+	err = wails.Run(&options.App{
+		Title:  "bill-manager-w",
 		Width:  1024,
 		Height: 768,
 		AssetServer: &assetserver.Options{
diff --git a/service.go b/service.go
new file mode 100644
index 0000000..6691f42
--- /dev/null
+++ b/service.go
@@ -0,0 +1,131 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+type BillService struct {
+	db    *DB
+	bills map[int64]Bill
+}
+
+const paymentColumns = "id, billid, monthFor, paymentDate"
+const billColumns = "id, name"
+
+func (s *BillService) GetPaymentsForDate(date time.Time) ([]Payment, error) {
+	res := []Payment{}
+	if s == nil {
+		return res, fmt.Errorf("calling GetPaymentsFor on nil BillService")
+	}
+	if s.db == nil || !s.db.Ready {
+		return res, fmt.Errorf("cannot get payments, db is nil or not ready - %v", s.db)
+	}
+
+	rows, err := s.db.readConn.Query(fmt.Sprintf(`
+SELECT %s
+FROM Payment
+WHERE monthFor = date(strftime('%%Y-%%m-01', ?));
+`, paymentColumns), date)
+	if err != nil {
+		return res, fmt.Errorf("query for payments of %s failed with error: %v", date, err)
+	}
+
+	for rows.Next() {
+		payment := Payment{}
+		err = rows.Scan(&payment.Id, &payment.BillId, &payment.MonthFor, &payment.PaymentDate)
+		if err != nil {
+			Error.Printf("failed to scan row: %v", err)
+			continue
+		}
+		res = append(res, payment)
+	}
+
+	return res, nil
+}
+
+func (s *BillService) GetPaymentForBillAndDate(billid int64, date time.Time) (Payment, error) {
+	res := Payment{}
+	if s == nil {
+		return res, fmt.Errorf("calling GetPaymentsFor on nil BillService")
+	}
+	if s.db == nil || !s.db.Ready {
+		return res, fmt.Errorf("cannot get payments, db is nil or not ready - %v", s.db)
+	}
+
+	row := s.db.readConn.QueryRow(fmt.Sprintf(`
+SELECT %s
+FROM Payment
+WHERE billid = ? AND monthFor = date(strftime('%%Y-%%m-01', ?));
+`, paymentColumns), billid, date)
+
+	err := row.Scan(&res.Id, &res.BillId, &res.MonthFor, &res.PaymentDate)
+	if err != nil {
+		return res, fmt.Errorf("failed scanning row: %v", err)
+	}
+
+	return res, nil
+}
+
+func (s *BillService) GetAllBills() ([]Bill, error) {
+	res := []Bill{}
+	if s == nil {
+		return res, fmt.Errorf("calling GetAllBills on nil BillService")
+	}
+	if s.db == nil || !s.db.Ready {
+		return res, fmt.Errorf("cannot get bills, db is nil or not ready - %v", s.db)
+	}
+
+	rows, err := s.db.readConn.Query(fmt.Sprintf(`SELECT %s FROM Bill ORDER BY name`, billColumns))
+	if err != nil {
+		return res, fmt.Errorf("failed to query for bills: %w", err)
+	}
+
+	for rows.Next() {
+		bill := Bill{}
+		err := rows.Scan(&bill.Id, &bill.Name)
+		if err != nil {
+			Error.Printf("failed to scan row: %v", err)
+			continue
+		}
+		res = append(res, bill)
+	}
+
+	s.bills = make(map[int64]Bill)
+	for _, bill := range res {
+		s.bills[bill.Id] = bill
+	}
+
+	return res, nil
+}
+
+func (s *BillService) MarkPaid(billid int64, monthFor time.Time, when time.Time) (Payment, error) {
+	res := Payment{}
+	if s == nil {
+		return res, fmt.Errorf("calling MarkPaid on nil BillService")
+	}
+	if s.db == nil || !s.db.Ready {
+		return res, fmt.Errorf("cannot mark bill paid, db is nil or not ready - %v", s.db)
+	}
+
+	qres, err := s.db.writeConn.Exec(`
+INSERT INTO Payment (billid, monthFor, paymentDate)
+VALUES (?, date(strftime('%Y-%m-01', ?)), ?)
+ON CONFLICT(billid, monthFor) DO UPDATE SET
+	paymentDate = excluded.paymentDate
+WHERE Payment.paymentDate IS NULL
+	`, billid, monthFor, when)
+	if err != nil {
+		return res, fmt.Errorf("failed upserting into payment with error: %w", err)
+	}
+
+	rows, err := qres.RowsAffected()
+	if err != nil {
+		return res, fmt.Errorf("failed to get rows affected: %w", err)
+	}
+	if rows == 0 {
+		return res, fmt.Errorf("no rows affected")
+	}
+
+	return s.GetPaymentForBillAndDate(billid, monthFor)
+}
diff --git a/types.go b/types.go
new file mode 100644
index 0000000..8b9d8d1
--- /dev/null
+++ b/types.go
@@ -0,0 +1,32 @@
+package main
+
+import "time"
+
+type (
+	Bill struct {
+		Id   int64
+		Name string
+	}
+	Payment struct {
+		Id          int64
+		BillId      int64
+		MonthFor    time.Time
+		PaymentDate time.Time
+	}
+
+	WailsBills struct {
+		Data    []Bill
+		Success bool
+		Error   string
+	}
+	WailsPayments struct {
+		Data    []Payment
+		Success bool
+		Error   string
+	}
+	WailsPayment struct {
+		Data    Payment
+		Success bool
+		Error   string
+	}
+)