You must do:
Upload 606 for the month 12/2010 with invoices received by January 15
File IT-1 for the month 12/2010 and pay any ITBIS due by January 20
Upload 607 invoices issued (comprobantes fiscales emitidos), before you file IR-2
Upload 608 (comprobantes fiscales anulados), before you file IR-2
File IR-2 with all annexes and pay taxes due by April 28. Annexes required: Activos, A-1, B-1, D, D-1, D-2, E where you select a respective cateory (comercio, or hoteles, or bancos y seguros).
Penalties for late payment are 11.93% first month (even one day after due date) and 5.93% the next month after, cumulative on the base amount due.
You must account for all invoices you issued to your customers in the month of 12/2010 for VAT (ITBIS) purposes and income tax purposes and count them as income regardless of whether you got the money from customers or not.
You must also pay assets tax, 1% of your assets, as determined by anexes "Activos" and "A-1" of IR-2 declaration.
