RCM ITC

i paid 2000/- Igst under RCM FOR THE MONTH OF JULY 2017,
AND I WILL PAY 2000/- IGST UNDER RCM FOR AUG'2017.I.E
I FILED 3B IN 3.1 POINT WITH 2000/-
AND ENTERD THE SAME AMOUNT IN 4TH POINT ELIGIBLE ITC, THEN IN 6TH POINT ENABLE WITH BALANCE OF 2000/- ,I OPENED THAT OFF SET MY PREVIOUS RCM ITC, BT SYSTEM SHOWS U HAVE NOT SUFFICIENT CASH/CREDIT, PLEASE CLARIFY IT.