Bill books come with duplicate and triplicate copies. Duplicate copy means it will be 1+1 booklet i.e. 1 parent copy and 1 duplicate copy. Triplicate copy means it will be 1+2 booklet i.e. 1 parent copy and 2 duplicate copies. Bill book standard size is A5 size. A4 size is the size of the normal photocopier paper. When A4 paper is folded from the center it becomes an A5 size paper, so A5 size is exactly half of an A4 paper. These books and vouches are widely used almost in all companies which have not yet shifted to POS invoicing system which generates the bill automatically.Proper maintenance of the record and no major qualification required for using bill books is another advantage. We can customize your order if you are looking for a thicker parent copy or duplicate.