21 = Demand Deposit Exception
22 = Demand Deposit
23 = Demand Deposit Prenotification
31 = Savings Deposit Exception
32 = Savings Deposit
33 = Savings Deposit Prenotification
26 = Demand Payment Exception
27 = Demand Payment
28 = Demand Payment Prenotification
36 = Savings Payment Exception
37 = Savings Payment
38 = Savings Payment Prenotification
41 = Automated General Ledger Deposit Exception or NOC for original transaction codes 42, 43, or 44
42 = Automated General Ledger Deposit (Credit)
43 = Prenotification of General Ledger Debit Authorization (non-dollar)
44 = Zero Dollar with remittance data (for CCD and CTX entries only)
46 = Automated General Ledger Payment Exception or NOC for original transaction codes 47, 48, or 49
47 = Automated General Ledger Deposit (Debit)
48 = Prenotification of General Ledger Debit Authorization (non-dollar)
49 = Zero Dollar with remittance data (for CCD and CTX entries only)
51 = Automated Loan Payment Exception or NOC for original transaction codes 52, 53, or 54
52 = Automated Loan Account Deposit (Credit)
53 = Prenotification of Loan Account Credit Authorization (non-dollar)
54 = Zero Dollar with remittance data (for CCD and CTX entries only; see Entry Class Code)
55 = Automated Loan Account Debit
56 = Automated Loan Payment Reversal Exception or NOC for original transaction code 55
source: fatwallet.com/t/52/701538/