On the contrary! Data for any month are entered into same table on same sheet! Only acceptable reason to have more entry sheets is part of entry data having different structure.

An example for need of several entry sheets may be e.g. Invoices handling workbook, where one entry sheet contains general invoice info (invoice number, invoice date, client name/id, etc.), and another entry sheet contains invoice details/row info (invoice number, invoice row number, article code, article unit price, quantity, etc.). And such workbook can have quite a number of various reports, like monthly/yearly totals, monthly/yearly totals for certain client, monthly/yearly totals for certain article, etc. Your imagination and skills, and the number of parameters your tables contain, are only limitations.