diff --git a/config/configuration.go b/config/configuration.go
index 6282bab1e..3a663fcea 100644
--- a/config/configuration.go
+++ b/config/configuration.go
@@ -467,6 +467,18 @@ const (
 	//  - N
 	ValidateFieldsHaveValues string = "ValidateFieldsHaveValues"
 
+	// ValidateChecksum if set to N, the checksum verification of incoming messages will be skipped.
+	// Useful when dealing with legacy systems or proxies that might malform the checksum.
+	//
+	// Required: No
+	//
+	// Default: Y
+	//
+	// Valid Values:
+	//  - Y
+	//  - N
+	ValidateChecksum string = "ValidateChecksum"
+
 	// CheckLatency if set to Y, messages must be received from the counter-party within a defined number of seconds.
 	// It is useful to turn this off if a system uses localtime for it's timestamps instead of GMT.
 	//
diff --git a/in_session.go b/in_session.go
index 0ed53200c..b0b9742b7 100644
--- a/in_session.go
+++ b/in_session.go
@@ -239,7 +239,8 @@ func (state inSession) resendMessages(session *session, beginSeqNo, endSeqNo int
 	nextSeqNum := seqNum
 	msg := NewMessage()
 	err := session.store.IterateMessages(beginSeqNo, endSeqNo, func(msgBytes []byte) error {
-		err := ParseMessageWithDataDictionary(msg, bytes.NewBuffer(msgBytes), session.transportDataDictionary, session.appDataDictionary)
+		skipChecksum := !session.SessionSettings.ValidateChecksum
+		err := ParseMessageWithDataDictionary(msg, bytes.NewBuffer(msgBytes), session.transportDataDictionary, session.appDataDictionary, skipChecksum)
 		if err != nil {
 			session.log.OnEventf("Resend Msg Parse Error: %v, %v", err.Error(), bytes.NewBuffer(msgBytes).String())
 			return err // We cant continue with a message that cant be parsed correctly.
diff --git a/internal/session_settings.go b/internal/session_settings.go
index c45134822..d1ee6f013 100644
--- a/internal/session_settings.go
+++ b/internal/session_settings.go
@@ -22,6 +22,7 @@ type SessionSettings struct {
 	ResetSeqTime                 time.Time
 	EnableResetSeqTime           bool
 	InChanCapacity               int
+	ValidateChecksum             bool
 
 	// Required on logon for FIX.T.1 messages.
 	DefaultApplVerID string
diff --git a/message.go b/message.go
index 35e2ff675..e33a9cfa8 100644
--- a/message.go
+++ b/message.go
@@ -38,6 +38,7 @@ type msgParser struct {
 	trailerBytes            []byte
 	foundBody               bool
 	foundTrailer            bool
+	skipChecksum            bool
 }
 
 // in the message header, the first 3 tags in the message header must be 8,9,35.
@@ -157,7 +158,7 @@ func (m *Message) CopyInto(to *Message) {
 
 // ParseMessage constructs a Message from a byte slice wrapping a FIX message.
 func ParseMessage(msg *Message, rawMessage *bytes.Buffer) (err error) {
-	return ParseMessageWithDataDictionary(msg, rawMessage, nil, nil)
+	return ParseMessageWithDataDictionary(msg, rawMessage, nil, nil, false)
 }
 
 // ParseMessageWithDataDictionary constructs a Message from a byte slice wrapping a FIX message using an optional session and application DataDictionary for reference.
@@ -166,12 +167,14 @@ func ParseMessageWithDataDictionary(
 	rawMessage *bytes.Buffer,
 	transportDataDictionary *datadictionary.DataDictionary,
 	appDataDictionary *datadictionary.DataDictionary,
+	skipChecksum bool,
 ) (err error) {
 	// Create msgparser before we go any further.
 	mp := &msgParser{
 		msg:                     msg,
 		transportDataDictionary: transportDataDictionary,
 		appDataDictionary:       appDataDictionary,
+		skipChecksum:            skipChecksum,
 	}
 	mp.msg.rawMessage = rawMessage
 	mp.rawBytes = rawMessage.Bytes()
@@ -297,8 +300,35 @@ func doParsing(mp *msgParser) (err error) {
 	bodyLength, err := mp.msg.Header.getIntNoLock(tagBodyLength)
 	if err != nil {
 		err = parseError{OrigError: err.Error()}
+		return
 	} else if length != bodyLength && !xmlDataMsg {
 		err = parseError{OrigError: fmt.Sprintf("Incorrect Message Length, expected %d, got %d", bodyLength, length)}
+		return
+	}
+
+	calculatedCheckSum := 0
+	for i := 0; i <= mp.fieldIndex; i++ {
+		if mp.msg.fields[i].tag == tagCheckSum {
+			continue
+		}
+		calculatedCheckSum += mp.msg.fields[i].total()
+	}
+
+	calculatedCheckSum = calculatedCheckSum % 256
+
+	if !mp.skipChecksum {
+		var expectedCheckSumStr string
+		expectedCheckSumStr, err = mp.msg.Trailer.getStringNoLock(tagCheckSum)
+		if err != nil {
+			err = parseError{OrigError: "CheckSum tag missing"}
+			return
+		}
+
+		if expectedCheckSumStr != formatCheckSum(calculatedCheckSum) {
+			err = parseError{
+				OrigError: fmt.Sprintf("Expected CheckSum=%s, Received CheckSum=%s", formatCheckSum(calculatedCheckSum), expectedCheckSumStr),
+			}
+		}
 	}
 
 	return
diff --git a/message_router_test.go b/message_router_test.go
index b2e7b59f5..1b1f8f7e4 100644
--- a/message_router_test.go
+++ b/message_router_test.go
@@ -115,7 +115,7 @@ func (suite *MessageRouterTestSuite) SetupTest() {
 }
 
 func (suite *MessageRouterTestSuite) TestNoRoute() {
-	suite.givenTheMessage([]byte("8=FIX.4.3
9=87
35=D
49=TW
34=3
56=ISLD
52=20160421-14:43:50
40=1
60=20160421-14:43:50
54=1
21=3
11=id
10=235
"))
+	suite.givenTheMessage([]byte("8=FIX.4.3
9=87
35=D
49=TW
34=3
56=ISLD
52=20160421-14:43:50
40=1
60=20160421-14:43:50
54=1
21=3
11=id
10=236
"))
 
 	rej := suite.Route(suite.msg, suite.sessionID)
 	suite.verifyMessageNotRouted()
@@ -123,17 +123,29 @@ func (suite *MessageRouterTestSuite) TestNoRoute() {
 }
 
 func (suite *MessageRouterTestSuite) TestNoRouteWhitelistedMessageTypes() {
-	var tests = []string{"0", "A", "1", "2", "3", "4", "5", "j"}
+	var tests = []struct {
+		msgType  string
+		checksum string
+	}{
+		{"0", "216"},
+		{"A", "233"},
+		{"1", "217"},
+		{"2", "218"},
+		{"3", "219"},
+		{"4", "220"},
+		{"5", "221"},
+		{"j", "018"},
+	}
 
 	for _, test := range tests {
 		suite.SetupTest()
 
-		msg := fmt.Sprintf("8=FIX.4.3
9=87
35=%v
49=TW
34=3
56=ISLD
52=20160421-14:43:50
40=1
60=20160421-14:43:50
54=1
21=3
11=id
10=235
", test)
+		msg := fmt.Sprintf("8=FIX.4.3
9=87
35=%s
49=TW
34=3
56=ISLD
52=20160421-14:43:50
40=1
60=20160421-14:43:50
54=1
21=3
11=id
10=%s
", test.msgType, test.checksum)
 		suite.givenTheMessage([]byte(msg))
 
 		rej := suite.Route(suite.msg, suite.sessionID)
 		suite.verifyMessageNotRouted()
-		suite.Nil(rej, "Message type '%v' should not be rejected by the MessageRouter", test)
+		suite.Nil(rej, "Message type '%s' should not be rejected by the MessageRouter", test.msgType)
 	}
 }
 
@@ -174,7 +186,7 @@ func (suite *MessageRouterTestSuite) TestRouteFIXT50AppWithApplVerID() {
 	suite.givenTheRoute(ApplVerIDFIX50, "D")
 	suite.givenTheRoute(ApplVerIDFIX50SP1, "D")
 
-	suite.givenTheMessage([]byte("8=FIXT.1.1
9=89
35=D
49=TW
34=3
56=ISLD
52=20160424-16:48:26
1128=7
40=1
60=20160424-16:48:26
11=id
21=3
10=120
"))
+	suite.givenTheMessage([]byte("8=FIXT.1.1
9=89
35=D
49=TW
34=3
56=ISLD
52=20160424-16:48:26
1128=7
40=1
60=20160424-16:48:26
11=id
21=3
10=192
"))
 	rej := suite.Route(suite.msg, suite.sessionID)
 	suite.verifyMessageRoutedBy(ApplVerIDFIX50, "D")
 	suite.Nil(rej)
@@ -185,7 +197,7 @@ func (suite *MessageRouterTestSuite) TestRouteFIXTAppWithApplVerID() {
 	suite.givenTheRoute(ApplVerIDFIX50, "D")
 	suite.givenTheRoute(ApplVerIDFIX50SP1, "D")
 
-	suite.givenTheMessage([]byte("8=FIXT.1.1
9=89
35=D
49=TW
34=3
56=ISLD
52=20160424-16:48:26
1128=8
40=1
60=20160424-16:48:26
11=id
21=3
10=120
"))
+	suite.givenTheMessage([]byte("8=FIXT.1.1
9=89
35=D
49=TW
34=3
56=ISLD
52=20160424-16:48:26
1128=8
40=1
60=20160424-16:48:26
11=id
21=3
10=193
"))
 	rej := suite.Route(suite.msg, suite.sessionID)
 	suite.verifyMessageRoutedBy(ApplVerIDFIX50SP1, "D")
 	suite.Nil(rej)
diff --git a/message_test.go b/message_test.go
index b02508cd9..ff05e99e0 100644
--- a/message_test.go
+++ b/message_test.go
@@ -65,7 +65,7 @@ func (s *MessageSuite) TestParseMessageEmpty() {
 }
 
 func (s *MessageSuite) TestParseMessage() {
-	rawMsg := bytes.NewBufferString("8=FIX.4.2
9=104
35=D
34=2
49=TW
52=20140515-19:49:56.659
56=ISLD
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
10=039
")
+	rawMsg := bytes.NewBufferString("8=FIX.4.2
9=104
35=D
34=2
49=TW
52=20140515-19:49:56.659
56=ISLD
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
10=051
")
 
 	err := ParseMessage(s.msg, rawMsg)
 	s.Nil(err)
@@ -99,14 +99,30 @@ func (s *MessageSuite) TestParseMessageWithDataDictionary() {
 			5050: nil,
 		},
 	}
-	rawMsg := bytes.NewBufferString("8=FIX.4.2
9=126
35=D
34=2
49=TW
52=20140515-19:49:56.659
56=ISLD
10030=CUST
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
5050=HELLO
10=039
")
+	rawMsg := bytes.NewBufferString("8=FIX.4.2
9=126
35=D
34=2
49=TW
52=20140515-19:49:56.659
56=ISLD
10030=CUST
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
5050=HELLO
10=036
")
 
-	err := ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict)
+	err := ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false)
 	s.Nil(err)
 	s.FieldEquals(Tag(10030), "CUST", s.msg.Header)
 	s.FieldEquals(Tag(5050), "HELLO", s.msg.Trailer)
 }
 
+func (s *MessageSuite) TestParseMessageSkipChecksum() {
+	rawMsg := bytes.NewBufferString("8=FIX.4.2
9=126
35=D
34=2
49=TW
52=20140515-19:49:56.659
56=ISLD
10030=CUST
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
5050=HELLO
10=035
")
+
+	// Test Strict Mode (skipChecksum = false) -> Should Fail
+	err := ParseMessageWithDataDictionary(s.msg, rawMsg, nil, nil, false)
+	s.NotNil(err, "Expected error when validating invalid checksum")
+	s.Contains(err.Error(), "Expected CheckSum")
+
+	// Test Lenient Mode (skipChecksum = true) -> Should Pass
+	s.msg = NewMessage()
+	rawMsg = bytes.NewBufferString("8=FIX.4.2
9=126
35=D
34=2
49=TW
52=20140515-19:49:56.659
56=ISLD
10030=CUST
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
5050=HELLO
10=035
")
+
+	err = ParseMessageWithDataDictionary(s.msg, rawMsg, nil, nil, true)
+	s.Nil(err, "Expected no error when skipping checksum validation")
+}
+
 func (s *MessageSuite) TestParseOutOfOrder() {
 	// Allow fields out of order, save for validation.
 	rawMsg := bytes.NewBufferString("8=FIX.4.0
9=81
35=D
11=id
21=3
38=100
40=1
54=1
55=MSFT
34=2
49=TW
52=20140521-22:07:09
56=ISLD
10=250
")
@@ -127,7 +143,7 @@ func (s *MessageSuite) TestBuild() {
 }
 
 func (s *MessageSuite) TestReBuild() {
-	rawMsg := bytes.NewBufferString("8=FIX.4.2
9=104
35=D
34=2
49=TW
52=20140515-19:49:56.659
56=ISLD
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
10=039
")
+	rawMsg := bytes.NewBufferString("8=FIX.4.2
9=104
35=D
34=2
49=TW
52=20140515-19:49:56.659
56=ISLD
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
10=051
")
 
 	s.Nil(ParseMessage(s.msg, rawMsg))
 
@@ -157,7 +173,7 @@ func (s *MessageSuite) TestRebuildOneRepeatingGroupWithDictionary() {
 			"10=026
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -178,7 +194,7 @@ func (s *MessageSuite) TestRebuildTwoRepeatingGroupsWithDictionary() {
 	rawMsg := bytes.NewBufferString("8=FIX.4.4
9=210
35=D
34=2
347=UTF-8
52=20231231-20:19:41
49=01001
50=01001a
56=TEST
44=12
11=13976
1=10100400
21=1
386=1
336=NOPL
55=SYMABC
54=1
60=20231231-20:19:41
38=1
40=2
59=0
453=1
448=4501
447=D
452=28
354=6
355=Public
10=104
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -199,7 +215,7 @@ func (s *MessageSuite) TestRebuildOneRepeatingGroupWithTwoMembersWithDictionary(
 			"10=044
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -223,7 +239,7 @@ func (s *MessageSuite) TestRebuildTwoSequentialRepeatingGroupWithDictionary() {
 			"10=243
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -248,7 +264,7 @@ func (s *MessageSuite) TestRebuildNestedRepeatingGroupWithDictionary() {
 			"10=206
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -273,7 +289,7 @@ func (s *MessageSuite) TestRebuildDoubleNestedRepeatingGroupWithDictionary() {
 			"10=117
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -298,7 +314,7 @@ func (s *MessageSuite) TestRebuildDoubleNestedThenAnotherRepeatingGroupWithDicti
 			"10=106
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -323,7 +339,7 @@ func (s *MessageSuite) TestRebuildDoubleNestedThenBodyTagThenAnotherRepeatingGro
 			"10=198
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -368,7 +384,7 @@ func (s *MessageSuite) TestRebuildDoubleNestedWithTwoMembersRepeatingGroupWithDi
 			"10=046
")
 
 	// When we parse it into a message
-	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict))
+	s.Nil(ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict, false))
 
 	// And then rebuild the message bytes
 	rebuildBytes := s.msg.build()
@@ -419,7 +435,7 @@ func (s *MessageSuite) TestReBuildWithRepeatingGroupForResend() {
 }
 
 func (s *MessageSuite) TestReverseRoute() {
-	s.Nil(ParseMessage(s.msg, bytes.NewBufferString("8=FIX.4.2
9=171
35=D
34=2
49=TW
50=KK
52=20060102-15:04:05
56=ISLD
57=AP
144=BB
115=JCD
116=CS
128=MG
129=CB
142=JV
143=RY
145=BH
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=123
")))
+	s.Nil(ParseMessage(s.msg, bytes.NewBufferString("8=FIX.4.2
9=171
35=D
34=2
49=TW
50=KK
52=20060102-15:04:05
56=ISLD
57=AP
144=BB
115=JCD
116=CS
128=MG
129=CB
142=JV
143=RY
145=BH
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=033
")))
 
 	builder := s.msg.reverseRoute()
 
@@ -450,7 +466,7 @@ func (s *MessageSuite) TestReverseRoute() {
 }
 
 func (s *MessageSuite) TestReverseRouteIgnoreEmpty() {
-	s.Nil(ParseMessage(s.msg, bytes.NewBufferString("8=FIX.4.0
9=128
35=D
34=2
49=TW
52=20060102-15:04:05
56=ISLD
115=
116=CS
128=MG
129=CB
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=123
")))
+	s.Nil(ParseMessage(s.msg, bytes.NewBufferString("8=FIX.4.0
9=128
35=D
34=2
49=TW
52=20060102-15:04:05
56=ISLD
115=
116=CS
128=MG
129=CB
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=041
")))
 	builder := s.msg.reverseRoute()
 
 	s.False(builder.Header.Has(tagDeliverToCompID), "Should not reverse if empty")
@@ -458,7 +474,7 @@ func (s *MessageSuite) TestReverseRouteIgnoreEmpty() {
 
 func (s *MessageSuite) TestReverseRouteFIX40() {
 	// The onbehalfof/deliverto location id not supported in fix 4.0.
-	s.Nil(ParseMessage(s.msg, bytes.NewBufferString("8=FIX.4.0
9=171
35=D
34=2
49=TW
50=KK
52=20060102-15:04:05
56=ISLD
57=AP
144=BB
115=JCD
116=CS
128=MG
129=CB
142=JV
143=RY
145=BH
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=123
")))
+	s.Nil(ParseMessage(s.msg, bytes.NewBufferString("8=FIX.4.0
9=171
35=D
34=2
49=TW
50=KK
52=20060102-15:04:05
56=ISLD
57=AP
144=BB
115=JCD
116=CS
128=MG
129=CB
142=JV
143=RY
145=BH
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=031
")))
 
 	builder := s.msg.reverseRoute()
 
@@ -468,7 +484,7 @@ func (s *MessageSuite) TestReverseRouteFIX40() {
 }
 
 func (s *MessageSuite) TestCopyIntoMessage() {
-	msgString := "8=FIX.4.2
9=171
35=D
34=2
49=TW
50=KK
52=20060102-15:04:05
56=ISLD
57=AP
144=BB
115=JCD
116=CS
128=MG
129=CB
142=JV
143=RY
145=BH
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=123
"
+	msgString := "8=FIX.4.2
9=171
35=D
34=2
49=TW
50=KK
52=20060102-15:04:05
56=ISLD
57=AP
144=BB
115=JCD
116=CS
128=MG
129=CB
142=JV
143=RY
145=BH
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=033
"
 	msgBuf := bytes.NewBufferString(msgString)
 	s.Nil(ParseMessage(s.msg, msgBuf))
 
diff --git a/repeating_group_test.go b/repeating_group_test.go
index abd316d78..e7d5db481 100644
--- a/repeating_group_test.go
+++ b/repeating_group_test.go
@@ -230,7 +230,7 @@ func TestRepeatingGroup_ReadRecursive(t *testing.T) {
 
 func TestRepeatingGroup_ReadComplete(t *testing.T) {
 
-	rawMsg := bytes.NewBufferString("8=FIXT.1.1
9=268
35=W
34=7118
49=TEST
52=20151027-18:41:52.698
56=TST
22=99
48=TSTX15
262=7
268=4
269=4
270=0.07499
272=20151027
273=18:41:52.698
269=7
270=0.07501
272=20151027
273=18:41:52.698
269=8
270=0.07494
272=20151027
273=18:41:52.698
269=B
271=60
272=20151027
273=18:41:52.698
10=163
")
+	rawMsg := bytes.NewBufferString("8=FIXT.1.1
9=268
35=W
34=7118
49=TEST
52=20151027-18:41:52.698
56=TST
22=99
48=TSTX15
262=7
268=4
269=4
270=0.07499
272=20151027
273=18:41:52.698
269=7
270=0.07501
272=20151027
273=18:41:52.698
269=8
270=0.07494
272=20151027
273=18:41:52.698
269=B
271=60
272=20151027
273=18:41:52.698
10=094
")
 
 	msg := NewMessage()
 	err := ParseMessage(msg, rawMsg)
diff --git a/session_factory.go b/session_factory.go
index 1b79f5ee1..2ace30a9e 100644
--- a/session_factory.go
+++ b/session_factory.go
@@ -216,6 +216,14 @@ func (f sessionFactory) newSession(
 		}
 	}
 
+	if settings.HasSetting(config.ValidateChecksum) {
+		if s.ValidateChecksum, err = settings.BoolSetting(config.ValidateChecksum); err != nil {
+			return
+		}
+	} else {
+		s.ValidateChecksum = true
+	}
+
 	if settings.HasSetting(config.CheckLatency) {
 		var doCheckLatency bool
 		if doCheckLatency, err = settings.BoolSetting(config.CheckLatency); err != nil {
diff --git a/session_factory_test.go b/session_factory_test.go
index 349e7580c..1731f5e71 100644
--- a/session_factory_test.go
+++ b/session_factory_test.go
@@ -426,6 +426,32 @@ func (s *SessionFactorySuite) TestStartEndDayWithWeekdaysError() {
 	s.NotNil(err)
 }
 
+func (s *SessionFactorySuite) TestValidateChecksum() {
+	var tests = []struct {
+		setting  string
+		expected bool
+	}{
+		{"Y", true},
+		{"N", false},
+	}
+
+	for _, test := range tests {
+		s.SetupTest()
+		s.SessionSettings.Set(config.ValidateChecksum, test.setting)
+
+		session, err := s.newSession(s.SessionID, s.MessageStoreFactory, s.SessionSettings, s.LogFactory, s.App)
+		s.Nil(err)
+		s.NotNil(session)
+
+		s.Equal(test.expected, session.ValidateChecksum, "Failed to set ValidateChecksum from config")
+	}
+
+	s.SetupTest()
+	session, err := s.newSession(s.SessionID, s.MessageStoreFactory, s.SessionSettings, s.LogFactory, s.App)
+	s.Nil(err)
+	s.True(session.ValidateChecksum, "Default ValidateChecksum should be true")
+}
+
 func (s *SessionFactorySuite) TestDefaultApplVerID() {
 	s.SessionID = SessionID{BeginString: BeginStringFIXT11, TargetCompID: "TW", SenderCompID: "ISLD"}
 
diff --git a/session_state.go b/session_state.go
index 6fe4dded7..e32d61ee5 100644
--- a/session_state.go
+++ b/session_state.go
@@ -92,7 +92,8 @@ func (sm *stateMachine) Incoming(session *session, m fixIn) {
 	session.log.OnIncoming(m.bytes.Bytes())
 
 	msg := NewMessage()
-	if err := ParseMessageWithDataDictionary(msg, m.bytes, session.transportDataDictionary, session.appDataDictionary); err != nil {
+	skipChecksum := !session.SessionSettings.ValidateChecksum
+	if err := ParseMessageWithDataDictionary(msg, m.bytes, session.transportDataDictionary, session.appDataDictionary, skipChecksum); err != nil {
 		session.log.OnEventf("Msg Parse Error: %v, %q", err.Error(), m.bytes)
 	} else {
 		msg.ReceiveTime = m.receiveTime
diff --git a/session_test.go b/session_test.go
index 2ea5c3508..aa3ca76e9 100644
--- a/session_test.go
+++ b/session_test.go
@@ -544,6 +544,29 @@ func (s *SessionSuite) TestIncomingNotInSessionTime() {
 	}
 }
 
+func (s *SessionSuite) TestIncomingValidateChecksum() {
+	s.session.State = inSession{}
+	s.Require().Nil(s.session.store.Reset())
+
+	msg := s.NewOrderSingle()
+	msg.Header.SetField(tagMsgSeqNum, FIXInt(1))
+	msgBytes := msg.build()
+
+	// Corrupt the checksum in the bytes directly
+	// The message ends with "10=XXX\x01". We flip a bit in the last digit.
+	checksumDigitIndex := len(msgBytes) - 2
+	msgBytes[checksumDigitIndex] ^= 1
+
+	s.session.ValidateChecksum = true
+	s.session.Incoming(s.session, fixIn{bytes: bytes.NewBuffer(msgBytes)})
+	s.MockApp.AssertNotCalled(s.T(), "FromApp")
+
+	s.session.ValidateChecksum = false
+	s.MockApp.On("FromApp").Return(nil)
+	s.session.Incoming(s.session, fixIn{bytes: bytes.NewBuffer(msgBytes)})
+	s.MockApp.AssertExpectations(s.T())
+}
+
 func (s *SessionSuite) TestSendAppMessagesNotInSessionTime() {
 	var tests = []struct {
 		before           sessionState
diff --git a/validation_test.go b/validation_test.go
index 7973464d1..e8ec8e4e3 100644
--- a/validation_test.go
+++ b/validation_test.go
@@ -20,8 +20,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/stretchr/testify/assert"
-
 	"github.com/quickfixgo/quickfix/datadictionary"
 )
 
@@ -32,6 +30,7 @@ type validateTest struct {
 	ExpectedRejectReason int
 	ExpectedRefTagID     *Tag
 	DoNotExpectReject    bool
+	ExpectParseError     bool
 }
 
 func TestValidate(t *testing.T) {
@@ -86,42 +85,54 @@ func TestValidate(t *testing.T) {
 		tcCheckUserDefinedFieldsDisabled(),
 		tcCheckUserDefinedFieldsDisabledFixT(),
 		tcMultipleRepeatingGroupFields(),
+		tcCheckSumValidation(),
 	}
 
 	msg := NewMessage()
 	for _, test := range tests {
-		assert.Nil(t, ParseMessage(msg, bytes.NewBuffer(test.MessageBytes)))
-		reject := test.Validator.Validate(msg)
+		t.Run(test.TestName, func(t *testing.T) {
+			err := ParseMessage(msg, bytes.NewBuffer(test.MessageBytes))
+
+			if test.ExpectParseError {
+				if err == nil {
+					t.Errorf("%v: Expected ParseMessage to fail, but it succeeded", test.TestName)
+				}
+				return
+			}
 
-		switch {
-		case reject == nil && test.DoNotExpectReject:
-			continue
+			if err != nil {
+				t.Fatalf("ParseMessage failed: %v", err)
+			}
+			reject := test.Validator.Validate(msg)
 
-		case reject != nil && test.DoNotExpectReject:
-			t.Errorf("%v: Unexpected reject: %v", test.TestName, reject)
-			continue
+			switch {
+			case reject == nil && test.DoNotExpectReject:
+				return
 
-		case reject == nil:
-			t.Errorf("%v: Expected reject", test.TestName)
-			continue
-		}
+			case reject != nil && test.DoNotExpectReject:
+				t.Errorf("%v: Unexpected reject: %v", test.TestName, reject)
+				return
 
-		if reject.RejectReason() != test.ExpectedRejectReason {
-			t.Errorf("%v: Expected reason %v got %v", test.TestName, test.ExpectedRejectReason, reject.RejectReason())
-		}
+			case reject == nil:
+				t.Errorf("%v: Expected reject", test.TestName)
+				return
+			}
 
-		switch {
-		case reject.RefTagID() == nil && test.ExpectedRefTagID == nil:
-		// OK, expected and actual ref tag not set.
-		case reject.RefTagID() != nil && test.ExpectedRefTagID == nil:
-			t.Errorf("%v: Unexpected RefTag '%v'", test.TestName, *reject.RefTagID())
-		case reject.RefTagID() == nil && test.ExpectedRefTagID != nil:
-			t.Errorf("%v: Expected RefTag '%v'", test.TestName, *test.ExpectedRefTagID)
-		case *reject.RefTagID() == *test.ExpectedRefTagID:
-			// OK, tags equal.
-		default:
-			t.Errorf("%v: Expected RefTag '%v' got '%v'", test.TestName, *test.ExpectedRefTagID, *reject.RefTagID())
-		}
+			if reject.RejectReason() != test.ExpectedRejectReason {
+				t.Errorf("%v: Expected reason %v got %v", test.TestName, test.ExpectedRejectReason, reject.RejectReason())
+			}
+
+			switch {
+			case reject.RefTagID() == nil && test.ExpectedRefTagID == nil:
+			case reject.RefTagID() != nil && test.ExpectedRefTagID == nil:
+				t.Errorf("%v: Unexpected RefTag '%v'", test.TestName, *reject.RefTagID())
+			case reject.RefTagID() == nil && test.ExpectedRefTagID != nil:
+				t.Errorf("%v: Expected RefTag '%v'", test.TestName, *test.ExpectedRefTagID)
+			case *reject.RefTagID() == *test.ExpectedRefTagID:
+			default:
+				t.Errorf("%v: Expected RefTag '%v' got '%v'", test.TestName, *test.ExpectedRefTagID, *reject.RefTagID())
+			}
+		})
 	}
 }
 
@@ -201,6 +212,7 @@ func tcInvalidTagNumberHeader() validateTest {
 	invalidHeaderFieldMessage := createFIX40NewOrderSingle()
 	tag := Tag(9999)
 	invalidHeaderFieldMessage.Header.SetField(tag, FIXString("hello"))
+	invalidHeaderFieldMessage.cook()
 	msgBytes := invalidHeaderFieldMessage.build()
 
 	return validateTest{
@@ -1109,7 +1121,7 @@ func tcTagAppearsMoreThanOnce() validateTest {
 	return validateTest{
 		TestName:             "Tag appears more than once",
 		Validator:            validator,
-		MessageBytes:         []byte("8=FIX.4.0
9=107
35=D
34=2
49=TW
52=20060102-15:04:05
56=ISLD
11=ID
21=1
40=1
40=2
54=1
38=200
55=INTC
60=20060102-15:04:05
10=234
"),
+		MessageBytes:         []byte("8=FIX.4.0
9=107
35=D
34=2
49=TW
52=20060102-15:04:05
56=ISLD
11=ID
21=1
40=1
40=2
54=1
38=200
55=INTC
60=20060102-15:04:05
10=166
"),
 		ExpectedRejectReason: rejectReasonTagAppearsMoreThanOnce,
 		ExpectedRefTagID:     &tag,
 	}
@@ -1124,7 +1136,7 @@ func tcTagAppearsMoreThanOnceFixT() validateTest {
 	return validateTest{
 		TestName:             "Tag appears more than once FIXT",
 		Validator:            validator,
-		MessageBytes:         []byte("8=FIXT.1.1
9=107
35=D
34=2
49=TW
52=20060102-15:04:05
56=ISLD
11=ID
21=1
40=1
40=2
54=1
38=200
55=INTC
60=20060102-15:04:05
10=234
"),
+		MessageBytes:         []byte("8=FIXT.1.1
9=107
35=D
34=2
49=TW
52=20060102-15:04:05
56=ISLD
11=ID
21=1
40=1
40=2
54=1
38=200
55=INTC
60=20060102-15:04:05
10=248
"),
 		ExpectedRejectReason: rejectReasonTagAppearsMoreThanOnce,
 		ExpectedRefTagID:     &tag,
 	}
@@ -1151,7 +1163,7 @@ func tcFloatValidationFixT() validateTest {
 	return validateTest{
 		TestName:             "FloatValidation FIXT",
 		Validator:            validator,
-		MessageBytes:         []byte("8=FIXT.1.1
9=106
35=D
34=2
49=TW
52=20140329-22:38:45
56=ISLD
11=ID
21=1
40=1
54=1
38=+200.00
55=INTC
60=20140329-22:38:45
10=178
"),
+		MessageBytes:         []byte("8=FIXT.1.1
9=106
35=D
34=2
49=TW
52=20140329-22:38:45
56=ISLD
11=ID
21=1
40=1
54=1
38=+200.00
55=INTC
60=20140329-22:38:45
10=002
"),
 		ExpectedRejectReason: rejectReasonIncorrectDataFormatForValue,
 		ExpectedRefTagID:     &tag,
 	}
@@ -1163,11 +1175,22 @@ func tcMultipleRepeatingGroupFields() validateTest {
 	return validateTest{
 		TestName:          "Multiple repeating group fields in a message",
 		Validator:         validator,
-		MessageBytes:      []byte("8=FIX.4.3
9=176
35=D
34=2
49=TW
52=20140329-22:38:45
56=ISLD
11=ID
453=2
448=PARTYID
452=3
523=SUBID
448=PARTYID2
452=3
78=1
79=ACCOUNT
80=1
21=1
40=1
54=1
38=200
55=INTC
60=20140329-22:38:45
10=178
"),
+		MessageBytes:      []byte("8=FIX.4.3
9=176
35=D
34=2
49=TW
52=20140329-22:38:45
56=ISLD
11=ID
453=2
448=PARTYID
452=3
523=SUBID
448=PARTYID2
452=3
78=1
79=ACCOUNT
80=1
21=1
40=1
54=1
38=200
55=INTC
60=20140329-22:38:45
10=012
"),
 		DoNotExpectReject: true,
 	}
 }
 
+func tcCheckSumValidation() validateTest {
+	dict, _ := datadictionary.Parse("spec/FIX43.xml")
+	validator := NewValidator(defaultValidatorSettings, dict, nil)
+	return validateTest{
+		TestName:         "Checksum is incorrect",
+		Validator:        validator,
+		MessageBytes:     []byte("8=FIX.4.3
9=176
35=D
34=2
49=TW
52=20140329-22:38:45
56=ISLD
11=ID
453=2
448=PARTYID
452=3
523=SUBID
448=PARTYID2
452=3
78=1
79=ACCOUNT
80=1
21=1
40=1
54=1
38=200
55=INTC
60=20140329-22:38:45
10=006
"),
+		ExpectParseError: true,
+	}
+}
+
 func TestValidateVisitField(t *testing.T) {
 	fieldType0 := datadictionary.NewFieldType("myfield", 11, "STRING")
 	fieldDef0 := &datadictionary.FieldDef{FieldType: fieldType0}