tax issue.

Hi,i have a quest about the tax thing,heres the background of my story..my place hv started the renovation a month ago..but its a big renovation so i gotta move out for a month.but i didnt notice that the tax department hv sent me the tax form already in like a month ago..so when i came back i found that im already late to send it back.this is my first time to get this form,so i have no idea what to do...should i call that number or just send it back immediately??thank you.