Difficult to reply without the actual data, but this works, if that's what you want:
[pre]
data t;
  CUS=1; ARREARS=1; INS=3; output;
  CUS=1; ARREARS=1; INS=1; output;
  CUS=2; ARREARS=1; INS=0; output;
run;
option nocenter formchar='|========================';
proc tabulate;
  class CUS;
  var ARREARS INS;
  table CUS, ARREARS*sum INS*sum ARREARS*pctsum
='Rate';
run;
===============================================================
|                      |  ARREARS   |    INS     |  ARREARS   |
|                      ========================================
|                      |    Sum     |    Sum     |    Rate    |
===============================================================
|CUS                   |            |            |            |
========================            |            |            |
|1                     |        2.00|        4.00|       50.00|
===============================================================
|2                     |        1.00|        0.00|           .|
===============================================================