diff --git a/Portifolio b/Portifolio
index 27919fc..bccb166 100755
Binary files a/Portifolio and b/Portifolio differ
diff --git a/app.db b/app.db
index 23f7672..4d8c3da 100644
Binary files a/app.db and b/app.db differ
diff --git a/internal/database/category.go b/internal/database/category.go
new file mode 100644
index 0000000..323ecc4
--- /dev/null
+++ b/internal/database/category.go
@@ -0,0 +1,54 @@
+package database
+
+import (
+	"Portifolio/internal/model"
+	"database/sql"
+	"fmt"
+)
+
+func InsertCategory(db *sql.DB, rc model.RevenueCategory) error {
+	if err := rc.Validate(false); err != nil {
+		return fmt.Errorf("failed to insert: %w", err)
+	}
+
+	company, err := GetCompanyByID(db, rc.CompanyID)
+	if err != nil {
+		return fmt.Errorf("failed to check company: %w", err)
+	}
+	if company == nil {
+		return fmt.Errorf("company %d not found", rc.CompanyID)
+	}
+
+	if rc.ParentID != nil && *rc.ParentID != 0 {
+		parent, err := GetCategoryByID(db, rc.CompanyID, *rc.ParentID)
+		if err != nil {
+			return fmt.Errorf("failed to check parent category: %w", err)
+		}
+		if parent == nil {
+			return fmt.Errorf("parent category %d not found", *rc.ParentID)
+		}
+	}
+
+	var parentID sql.NullInt64
+	if rc.ParentID != nil && *rc.ParentID != 0 {
+		parentID = sql.NullInt64{Int64: int64(*rc.ParentID), Valid: true}
+	}
+
+	_, err = db.Exec(
+		`INSERT INTO category (company_id, parent_id, name) VALUES (?, ?, ?)
+		 ON CONFLICT(company_id, name) DO UPDATE SET parent_id=excluded.parent_id`,
+		rc.CompanyID, parentID, rc.Name,
+	)
+	if err != nil {
+		return fmt.Errorf("upsert category: %w", err)
+	}
+
+	err = db.QueryRow(
+		`SELECT id FROM category WHERE company_id = ? AND name = ?`,
+		rc.CompanyID, rc.Name,
+	).Scan(&rc.ID)
+	if err != nil {
+		return fmt.Errorf("select category id: %w", err)
+	}
+	return nil
+}
diff --git a/internal/database/company.go b/internal/database/company.go
new file mode 100644
index 0000000..6be510c
--- /dev/null
+++ b/internal/database/company.go
@@ -0,0 +1,25 @@
+package database
+
+import (
+	"Portifolio/internal/model"
+	"database/sql"
+	"fmt"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func GetCompanyByID(db *sql.DB, id int) (*model.Company, error) {
+	var c model.Company
+	err := db.QueryRow(
+		`SELECT id, name, shares_outstanding, price, currency_id FROM companies WHERE id = ?`,
+		id,
+	).Scan(&c.ID, &c.Name, &c.SharesOutstanding, &c.Price, &c.CurrencyID)
+
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("query company: %w", err)
+	}
+	return &c, nil
+}
diff --git a/internal/database/currency.go b/internal/database/currency.go
new file mode 100644
index 0000000..e5d9fe0
--- /dev/null
+++ b/internal/database/currency.go
@@ -0,0 +1,21 @@
+package database
+
+import (
+	"Portifolio/internal/model"
+	"database/sql"
+	"fmt"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func GetCurrencyByID(db *sql.DB, ID int) (model.Currency, error) {
+	var c model.Currency
+	err := db.QueryRow(
+		`SELECT id, code, name, FROM currencies WHERE id = ?`,
+		ID,
+	).Scan(&c.ID, &c.Code, &c.Name)
+	if err == sql.ErrNoRows {
+		return c, fmt.Errorf("company %d not found", ID)
+	}
+	return c, nil
+}
diff --git a/internal/database/revenue.go b/internal/database/revenue.go
index fd59555..f76da0d 100644
--- a/internal/database/revenue.go
+++ b/internal/database/revenue.go
@@ -9,7 +9,23 @@ import (
 	_ "github.com/mattn/go-sqlite3"
 )
 
+func GetCategoryByID(db *sql.DB, companyID int, ID int) (*model.RevenueCategory, error) {
+	var rc model.RevenueCategory
+	err := db.QueryRow(
+		`SELECT id, company_id, parent_id, name FROM category WHERE company_id = ? AND id = ?`,
+		companyID, ID,
+	).Scan(&rc.ID, &rc.CompanyID, &rc.ParentID, &rc.Name)
+	if err == sql.ErrNoRows {
+		return &rc, fmt.Errorf("category %q not found for company %d", ID, companyID)
+	}
+	if err != nil {
+		return &rc, fmt.Errorf("get category by name: %w", err)
+	}
+	return &rc, nil
+}
+
 func GetCategoryByName(db *sql.DB, companyID int, name string) (model.RevenueCategory, error) {
+
 	var rc model.RevenueCategory
 	err := db.QueryRow(
 		`SELECT id, company_id, parent_id, name FROM category WHERE company_id = ? AND name = ?`,
diff --git a/internal/model/company.go b/internal/model/company.go
index 74ee95c..43d6bb4 100644
--- a/internal/model/company.go
+++ b/internal/model/company.go
@@ -6,7 +6,6 @@ type Company struct {
 	SharesOutstanding int
 	Price             float64
 	CurrencyID        int
-	Currency          *Currency // populated on joins
 }
 
 type CompanyInput struct {
diff --git a/internal/model/periode.go b/internal/model/periode.go
index c909907..6606900 100644
--- a/internal/model/periode.go
+++ b/internal/model/periode.go
@@ -2,10 +2,65 @@
 package model
 
 import (
+	"database/sql"
 	"fmt"
 	"time"
 )
 
+// PeriodType defines the granularity of the revenue entry
+type PeriodType string
+
+const (
+	PeriodQuarter  PeriodType = "Q"
+	PeriodHalfYear PeriodType = "H"
+	PeriodYear     PeriodType = "Y"
+)
+
+// Period holds the actual time range for a revenue entry
+type Period struct {
+	ID    int
+	Type  PeriodType
+	Year  int
+	Index int // Q1=1 Q2=2 Q3=3 Q4=4 | H1=1 H2=2 | FY=1
+	Start time.Time
+	End   time.Time
+}
+
+func (p *Period) Validate(checkID bool) error {
+	if p.ID == 0 && checkID {
+		return fmt.Errorf("No ID Set")
+	} else if p.Type == PeriodQuarter && (p.Index > 4 || p.Index < 1) {
+		return fmt.Errorf("Not Valid Quarter index")
+	} else if p.Type == PeriodHalfYear && (p.Index > 2 || p.Index < 1) {
+		return fmt.Errorf("Not Valid HalfYear index")
+	} else if p.Type == PeriodHalfYear && (p.Index != 1 || p.Year < 1) {
+		return fmt.Errorf("Not Valid Year index")
+	}
+	return nil
+}
+
+func (p *Period) Insert(db *sql.DB) error {
+	_, err := db.Exec(
+		`INSERT INTO periods (type, year, idx, start_date, end_date) VALUES (?, ?, ?, ?, ?)
+         ON CONFLICT(type, year, idx) DO UPDATE SET start_date=excluded.start_date, end_date=excluded.end_date`,
+		string(p.Type), p.Year, p.Index, p.Start.Format("2006-01-02"), p.End.Format("2006-01-02"),
+	)
+	if err != nil {
+		return fmt.Errorf("upsert period: %w", err)
+	}
+
+	var id int
+	err = db.QueryRow(
+		`SELECT id FROM periods WHERE type = ? AND year = ? AND idx = ?`,
+		string(p.Type), p.Year, p.Index,
+	).Scan(&id)
+	if err != nil {
+		return fmt.Errorf("select period: %w", err)
+	}
+	p.ID = id
+	return nil
+}
+
 func QuarterPeriod(year, q int) Period {
 	months := map[int][2]int{
 		1: {1, 3}, 2: {4, 6}, 3: {7, 9}, 4: {10, 12},
diff --git a/internal/model/revenue.go b/internal/model/revenue.go
index 70cc388..220288c 100644
--- a/internal/model/revenue.go
+++ b/internal/model/revenue.go
@@ -1,52 +1,9 @@
 package model
 
 import (
-	"database/sql"
 	"fmt"
-	"time"
 )
 
-// PeriodType defines the granularity of the revenue entry
-type PeriodType string
-
-const (
-	PeriodQuarter  PeriodType = "Q"
-	PeriodHalfYear PeriodType = "H"
-	PeriodYear     PeriodType = "Y"
-)
-
-// Period holds the actual time range for a revenue entry
-type Period struct {
-	ID    int
-	Type  PeriodType
-	Year  int
-	Index int // Q1=1 Q2=2 Q3=3 Q4=4 | H1=1 H2=2 | FY=1
-	Start time.Time
-	End   time.Time
-}
-
-func (p *Period) Insert(db *sql.DB) error {
-	_, err := db.Exec(
-		`INSERT INTO periods (type, year, idx, start_date, end_date) VALUES (?, ?, ?, ?, ?)
-         ON CONFLICT(type, year, idx) DO UPDATE SET start_date=excluded.start_date, end_date=excluded.end_date`,
-		string(p.Type), p.Year, p.Index, p.Start.Format("2006-01-02"), p.End.Format("2006-01-02"),
-	)
-	if err != nil {
-		return fmt.Errorf("upsert period: %w", err)
-	}
-
-	var id int
-	err = db.QueryRow(
-		`SELECT id FROM periods WHERE type = ? AND year = ? AND idx = ?`,
-		string(p.Type), p.Year, p.Index,
-	).Scan(&id)
-	if err != nil {
-		return fmt.Errorf("select period: %w", err)
-	}
-	p.ID = id
-	return nil
-}
-
 type RevenueCategory struct {
 	ID        int
 	CompanyID int
@@ -54,8 +11,8 @@ type RevenueCategory struct {
 	Name      string // e.g. "product", "location", "segment"
 }
 
-func (rc *RevenueCategory) Validate() error {
-	if rc.ID == 0 {
+func (rc *RevenueCategory) Validate(checkID bool) error {
+	if rc.ID == 0 && checkID {
 		return fmt.Errorf("No ID Set")
 	} else if rc.Name == "" {
 		return fmt.Errorf("No Name found")
@@ -65,31 +22,6 @@ func (rc *RevenueCategory) Validate() error {
 	return nil
 }
 
-func (rc *RevenueCategory) Insert(db *sql.DB) error {
-	if err := rc.Validate(); err != nil {
-		return fmt.Errorf("failed to insert: %w", err)
-	}
-
-	_, err := db.Exec(
-		`INSERT INTO category (company_id, parent_id, name) VALUES (?, ?, ?)
-		 ON CONFLICT(company_id, name) DO UPDATE SET parent_id=excluded.parent_id`,
-		rc.CompanyID, rc.ParentID, rc.Name,
-	)
-	if err != nil {
-		return fmt.Errorf("upsert category: %w", err)
-	}
-
-	err = db.QueryRow(
-		`SELECT id FROM category WHERE company_id = ? AND name = ?`,
-		rc.CompanyID, rc.Name,
-	).Scan(&rc.ID)
-	if err != nil {
-		return fmt.Errorf("select category id: %w", err)
-	}
-
-	return nil
-}
-
 // Revenue is a single line in a financial report
 type Revenue struct {
 	ID       int
diff --git a/internal/service/company.go b/internal/service/company.go
index e3c50a1..ed3ef16 100644
--- a/internal/service/company.go
+++ b/internal/service/company.go
@@ -43,7 +43,6 @@ func GetAllCompanies(db *sql.DB) ([]model.Company, error) {
 			return nil, err
 		}
 		c.CurrencyID = cu.ID
-		c.Currency = &cu
 		companies = append(companies, c)
 	}
 	return companies, rows.Err()
diff --git a/internal/service/revenue.go b/internal/service/revenue.go
index a103d87..b995b91 100644
--- a/internal/service/revenue.go
+++ b/internal/service/revenue.go
@@ -10,9 +10,19 @@ import (
 	_ "github.com/mattn/go-sqlite3"
 )
 
-func InsertRevenue(db *sql.DB, companyID, currencyID int, categoryName string, parentID *int, value float64, period model.Period) error {
+func InsertRevenue(db *sql.DB, companyID int, currencyID int, categoryName string, parentID *int, value float64, period model.Period) error {
+	_, err := database.GetCompanyByID(db, companyID)
+	if err != nil {
+		return err
+	}
 
-	period, err := database.GetPeriodByID(db, period.ID)
+	_, err = database.GetCurrencyByID(db, currencyID)
+	if err != nil {
+		return err
+	}
+
+	// checking if period is in db, in case not will insert
+	_, err = database.GetPeriodByID(db, period.ID)
 	if err != nil {
 		err = period.Insert(db)
 		if err != nil {
@@ -27,7 +37,7 @@ func InsertRevenue(db *sql.DB, companyID, currencyID int, categoryName string, p
 			ParentID:  parentID,
 			Name:      categoryName,
 		}
-		err := category.Insert(db)
+		err := database.InsertCategory(db, category)
 		if err != nil {
 			return err
 		}
diff --git a/internal/shell/company.go b/internal/shell/company.go
index 9a5d429..a3c1881 100644
--- a/internal/shell/company.go
+++ b/internal/shell/company.go
@@ -1,6 +1,7 @@
 package shell
 
 import (
+	"Portifolio/internal/database"
 	"Portifolio/internal/model"
 	"Portifolio/internal/service"
 	"bufio"
@@ -68,10 +69,13 @@ func ListCompanies(db *sql.DB) {
 	fmt.Printf("\n  %-5s %-20s %-10s %-15s %s\n", "ID", "NAME", "CURRENCY", "PRICE", "SHARES")
 	fmt.Println("  " + strings.Repeat("-", 60))
 	for _, c := range companies {
-		currency := "N/A"
-		if c.Currency != nil {
-			currency = c.Currency.Code
+
+		currency, err := database.GetCurrencyByID(db, c.CurrencyID)
+		if err != nil {
+			fmt.Println("No currency by id.")
+			return
 		}
+
 		fmt.Printf("  %-5d %-20s %-10s %-15.2f %d\n",
 			c.ID, c.Name, currency, c.Price, c.SharesOutstanding)
 	}
diff --git a/internal/shell/revenue.go b/internal/shell/revenue.go
index b50649e..3a05ae9 100644
--- a/internal/shell/revenue.go
+++ b/internal/shell/revenue.go
@@ -1,6 +1,7 @@
 package shell
 
 import (
+	"Portifolio/internal/database"
 	"Portifolio/internal/model"
 	"Portifolio/internal/service"
 	"bufio"
@@ -67,6 +68,12 @@ func AddRevenue(scanner *bufio.Scanner, db *sql.DB) {
 		fmt.Println("  ✗", err)
 		return
 	}
+	// checking if company exits
+	_, err = database.GetCompanyByID(db, companyID)
+	if err != nil {
+		fmt.Println("No company by that id:", err)
+		return
+	}
 	currencyID, err := promptInt(scanner, "  Currency ID: ")
 	if err != nil {
 		fmt.Println("  ✗", err)