20% itc limit

Out of my puchase itc of Rs. 10l, in my 2a itc reflected only Rs.9l. But as balance itc is in 20% limit I awailed whole Rs.10l credit in 1st month. In 2nd month should I check whether Rs 1l invoices not shown in 1st month shown 2nd month or I should ignore it as I took credit in 1st month. Means in 2nd month should I include 1st months not shown invoices Rs1l in calculating 20% limit of 2nd month i.e. 20% limit is for every month or cumulative of all not shown invoices till date.