In this specific situation CU*BASE automatically uses an IRA withdrawal and deposit code of I for both sides of the transfer.  There is no field currently on CU*BASE to specify an IRA withdrawal or deposit code. 
An I IRA deposit/withdrawal code is defined as follows:
Internal transfer from one IRA suffix to another within the same credit union (no effect on accumulators).  These transactions are not reported to the IRS.
A complete description of all IRA codes can be obtained via CU*BASE Online Help (use the link below).