Please excuse me that I write in English because my computer has no chinese software.
1). go to community centre for tax service, it's free
2). You can file 2005 tax return for one month only, i.e., December.
3). both you and your spouse should file tax return, and you can get tax package from post office (free): two people, two packages, two copies for each person.
4). it's better to file tax return than not. the deadline is April 30.
if you need more info. or help, send me email.
Good luck!