Er-1 help

Dear friends,

Suppose we have paid the excise duty payable for the month of of may during june. In that case while filling up (er-1) the  account current extract paid sheet  should we enter the amount paid in respect of excise duty towards the month of may (actually paid in june) or amount paid in may (i.e) april month's excise duty.

I have the same doubt in filling the challan details in the last page of the return. Kindly clarify. thanks in advance.