diff --git a/main.go b/main.go
index ea594a8..28f8db2 100644
--- a/main.go
+++ b/main.go
@@ -64,6 +64,7 @@ func main() {
 	servemux.HandleFunc("/user/", UserHandler)
 	servemux.HandleFunc("/security/", SecurityHandler)
 	servemux.HandleFunc("/account/", AccountHandler)
+	servemux.HandleFunc("/transaction/", TransactionHandler)
 
 	listener, err := net.Listen("tcp", ":"+strconv.Itoa(port))
 	if err != nil {
diff --git a/transactions.go b/transactions.go
index 8c68d05..89f048e 100644
--- a/transactions.go
+++ b/transactions.go
@@ -1,7 +1,12 @@
 package main
 
 import (
+	"encoding/json"
+	"errors"
+	"log"
 	"math/big"
+	"net/http"
+	"strings"
 	"time"
 )
 
@@ -11,10 +16,24 @@ type Split struct {
 	AccountId     int64
 	Number        int64 // Check or reference number
 	Memo          string
-	Amount        big.Rat
+	Amount        string // String representation of decimal, suitable for passing to big.Rat.SetString()
 	Debit         bool
 }
 
+func (s *Split) GetAmount() (*big.Rat, error) {
+	var r big.Rat
+	_, success := r.SetString(s.Amount)
+	if !success {
+		return nil, errors.New("Couldn't convert Split.Amount to big.Rat via SetString()")
+	}
+	return &r, nil
+}
+
+func (s *Split) Valid() bool {
+	_, err := s.GetAmount()
+	return err == nil
+}
+
 type TransactionStatus int64
 
 const (
@@ -30,4 +49,378 @@ type Transaction struct {
 	Description   string
 	Status        TransactionStatus
 	Date          time.Time
+	Splits        []*Split `db:"-"`
+}
+
+type TransactionList struct {
+	Transactions *[]Transaction `json:"transactions"`
+}
+
+func (t *Transaction) Write(w http.ResponseWriter) error {
+	enc := json.NewEncoder(w)
+	return enc.Encode(t)
+}
+
+func (t *Transaction) Read(json_str string) error {
+	dec := json.NewDecoder(strings.NewReader(json_str))
+	return dec.Decode(t)
+}
+
+func (tl *TransactionList) Write(w http.ResponseWriter) error {
+	enc := json.NewEncoder(w)
+	return enc.Encode(tl)
+}
+
+func (t *Transaction) Valid() bool {
+	for i := range t.Splits {
+		if !t.Splits[i].Valid() {
+			return false
+		}
+	}
+	return true
+}
+
+func (t *Transaction) Balanced() bool {
+	var zero, sum big.Rat
+	if !t.Valid() {
+		return false // TODO Open question: should we report an error here instead?
+	}
+	for i := range t.Splits {
+		amount, _ := t.Splits[i].GetAmount()
+		if t.Splits[i].Debit {
+			sum.Add(&sum, amount)
+		} else {
+			sum.Sub(&sum, amount)
+		}
+	}
+	return sum.Cmp(&zero) == 0
+}
+
+func GetTransaction(transactionid int64, userid int64) (*Transaction, error) {
+	var t Transaction
+
+	transaction, err := DB.Begin()
+	if err != nil {
+		return nil, err
+	}
+
+	err = transaction.SelectOne(&t, "SELECT * from transaction where UserId=? AND TransactionId=?", userid, transactionid)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = transaction.Select(&t.Splits, "SELECT * from splits where TransactionId=?", transactionid)
+	if err != nil {
+		return nil, err
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		transaction.Rollback()
+		return nil, err
+	}
+
+	return &t, nil
+}
+
+func GetTransactions(userid int64) (*[]Transaction, error) {
+	var transactions []Transaction
+
+	transaction, err := DB.Begin()
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = transaction.Select(&transactions, "SELECT * from transactions where UserId=?", userid)
+	if err != nil {
+		return nil, err
+	}
+
+	for i := range transactions {
+		_, err := transaction.Select(&transactions[i].Splits, "SELECT * from splits where TransactionId=?", transactions[i].TransactionId)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		transaction.Rollback()
+		return nil, err
+	}
+
+	return &transactions, nil
+}
+
+type AccountMissingError struct{}
+
+func (ame AccountMissingError) Error() string {
+	return "Account missing"
+}
+
+func InsertTransaction(t *Transaction) error {
+	transaction, err := DB.Begin()
+	if err != nil {
+		return err
+	}
+
+	for i := range t.Splits {
+		existing, err := transaction.SelectInt("SELECT count(*) from accounts where AccountId=?", t.Splits[i].AccountId)
+		if err != nil {
+			transaction.Rollback()
+			return err
+		}
+		if existing != 1 {
+			transaction.Rollback()
+			return AccountMissingError{}
+		}
+	}
+
+	err = transaction.Insert(t)
+	if err != nil {
+		transaction.Rollback()
+		return err
+	}
+
+	for i := range t.Splits {
+		t.Splits[i].TransactionId = t.TransactionId
+		t.Splits[i].SplitId = -1
+		err = transaction.Insert(t.Splits[i])
+		if err != nil {
+			transaction.Rollback()
+			return err
+		}
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		transaction.Rollback()
+		return err
+	}
+
+	return nil
+}
+
+func UpdateTransaction(t *Transaction) error {
+	transaction, err := DB.Begin()
+	if err != nil {
+		return err
+	}
+
+	var existing_splits []*Split
+
+	_, err = transaction.Select(&existing_splits, "SELECT * from splits where TransactionId=?", t.TransactionId)
+	if err != nil {
+		transaction.Rollback()
+		return err
+	}
+
+	// Make a map with any existing splits for this transaction
+	m := make(map[int64]int64)
+	for i := range existing_splits {
+		m[existing_splits[i].SplitId] = existing_splits[i].SplitId
+	}
+
+	// Insert splits, updating any pre-existing ones
+	for i := range t.Splits {
+		t.Splits[i].TransactionId = t.TransactionId
+		_, ok := m[t.Splits[i].SplitId]
+		if ok {
+			count, err := transaction.Update(t.Splits[i])
+			if err != nil {
+				transaction.Rollback()
+				return err
+			}
+			if count != 1 {
+				transaction.Rollback()
+				return errors.New("Updated more than one transaction split")
+			}
+		} else {
+			t.Splits[i].SplitId = -1
+			err := transaction.Insert(t.Splits[i])
+			if err != nil {
+				transaction.Rollback()
+				return err
+			}
+		}
+	}
+
+	// Delete any remaining pre-existing splits
+	for i := range existing_splits {
+		s, ok := m[existing_splits[i].SplitId]
+		if ok {
+			_, err := transaction.Delete(s)
+			if err != nil {
+				transaction.Rollback()
+				return err
+			}
+		}
+	}
+
+	count, err := transaction.Update(t)
+	if err != nil {
+		transaction.Rollback()
+		return err
+	}
+	if count != 1 {
+		transaction.Rollback()
+		return errors.New("Updated more than one transaction")
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		transaction.Rollback()
+		return err
+	}
+
+	return nil
+}
+
+func TransactionHandler(w http.ResponseWriter, r *http.Request) {
+	user, err := GetUserFromSession(r)
+	if err != nil {
+		WriteError(w, 1 /*Not Signed In*/)
+		return
+	}
+
+	if r.Method == "POST" {
+		transaction_json := r.PostFormValue("transaction")
+		if transaction_json == "" {
+			WriteError(w, 3 /*Invalid Request*/)
+			return
+		}
+
+		var transaction Transaction
+		err := transaction.Read(transaction_json)
+		if err != nil {
+			WriteError(w, 3 /*Invalid Request*/)
+			return
+		}
+		transaction.TransactionId = -1
+		transaction.UserId = user.UserId
+
+		if !transaction.Valid() || !transaction.Balanced() {
+			WriteError(w, 3 /*Invalid Request*/)
+			return
+		}
+
+		for i := range transaction.Splits {
+			transaction.Splits[i].SplitId = -1
+			_, err := GetAccount(transaction.Splits[i].AccountId, user.UserId)
+			if err != nil {
+				WriteError(w, 3 /*Invalid Request*/)
+				return
+			}
+		}
+
+		err = InsertTransaction(&transaction)
+		if err != nil {
+			if _, ok := err.(AccountMissingError); ok {
+				WriteError(w, 3 /*Invalid Request*/)
+			} else {
+				WriteError(w, 999 /*Internal Error*/)
+				log.Print(err)
+			}
+			return
+		}
+
+		WriteSuccess(w)
+	} else if r.Method == "GET" {
+		transactionid, err := GetURLID(r.URL.Path)
+		if err != nil {
+			//Return all Transactions
+			var al TransactionList
+			transactions, err := GetTransactions(user.UserId)
+			if err != nil {
+				WriteError(w, 999 /*Internal Error*/)
+				log.Print(err)
+				return
+			}
+			al.Transactions = transactions
+			err = (&al).Write(w)
+			if err != nil {
+				WriteError(w, 999 /*Internal Error*/)
+				log.Print(err)
+				return
+			}
+		} else {
+			//Return Transaction with this Id
+			transaction, err := GetTransaction(transactionid, user.UserId)
+			if err != nil {
+				WriteError(w, 3 /*Invalid Request*/)
+				return
+			}
+			err = transaction.Write(w)
+			if err != nil {
+				WriteError(w, 999 /*Internal Error*/)
+				log.Print(err)
+				return
+			}
+		}
+	} else {
+		transactionid, err := GetURLID(r.URL.Path)
+		if err != nil {
+			WriteError(w, 3 /*Invalid Request*/)
+			return
+		}
+		if r.Method == "PUT" {
+			transaction_json := r.PostFormValue("transaction")
+			if transaction_json == "" {
+				WriteError(w, 3 /*Invalid Request*/)
+				return
+			}
+
+			var transaction Transaction
+			err := transaction.Read(transaction_json)
+			if err != nil || transaction.TransactionId != transactionid {
+				WriteError(w, 3 /*Invalid Request*/)
+				return
+			}
+			transaction.UserId = user.UserId
+
+			if !transaction.Valid() || !transaction.Balanced() {
+				WriteError(w, 3 /*Invalid Request*/)
+				return
+			}
+
+			for i := range transaction.Splits {
+				transaction.Splits[i].SplitId = -1
+				_, err := GetAccount(transaction.Splits[i].AccountId, user.UserId)
+				if err != nil {
+					WriteError(w, 3 /*Invalid Request*/)
+					return
+				}
+			}
+
+			err = UpdateTransaction(&transaction)
+			if err != nil {
+				WriteError(w, 999 /*Internal Error*/)
+				log.Print(err)
+				return
+			}
+
+			WriteSuccess(w)
+		} else if r.Method == "DELETE" {
+			transactionid, err := GetURLID(r.URL.Path)
+			if err != nil {
+				WriteError(w, 3 /*Invalid Request*/)
+				return
+			}
+
+			transaction, err := GetTransaction(transactionid, user.UserId)
+			if err != nil {
+				WriteError(w, 3 /*Invalid Request*/)
+				return
+			}
+
+			count, err := DB.Delete(&transaction)
+			if count != 1 || err != nil {
+				WriteError(w, 999 /*Internal Error*/)
+				log.Print(err)
+				return
+			}
+
+			WriteSuccess(w)
+		}
+	}
 }