Checked your mailbox this week?

The 2011 census package began arriving in mailboxes across the country this week. But it's the six little words on the front of the envelope that are irritating some Canadians.

"Complete the census -- it's the law" read the words.

Following the census flap last year, many Canadians appear to be under the mistaken impression that the census is no longer mandatory.

In fact, the Conservative government scrapped the mandatory long-form census, but the short form, which collects basic demographic information, is still mandatory.

It seems that many Canadians aren't pleased, taking to the Web to express irritation.

One reader in Manitoba wrote into to say, "Completing census forms should be voluntary, not threathening us that it's compulsory 'by law'. This is another gov't invasion of my privacy - the gov't already has all the information; doesn't have to snoop for more ... Disgusted!"

On Twitter, Luc Leger under the handle fredydose writes: "I hear the census is mandatory, then why the hell isn't voting mandatory as well? #changeisneeded in Canada."

Plenty of others are bemoaning the death of the long-form census, which many insist is the only way to acquire reliable data.

"Short form #census has a comments field at the end to address concerns. Voice your feelings on long form" urges Bharat C under the handle oliveridley.

Tony Clement cheekily weighed in Tuesday: "Just a reminder to Canadian tweeps to fill out your Census &/or Survey form. Sincerely, me, the Minister resp for StatsCan," he tweeted.

Canadians are required to fill out the census form within 10 days or receiving it, either online or by returning the paper copy by mail. The online site claims that it shouldn't take more than 10 minutes to fill out.

The census is conducted every five years and asks about the number of people living in the household, their names, their marital status, their language and consent to release personal information after 92 years.

Statistics Canada encourages all household to complete the census, noting that census information is vital for planning services, such as schools, daycare, police and fire.

This year, one in every three households will be asked to fill out a National Household Survey, which is the government's replacement to the long-form census.

The Conservative government eliminated the long-form census last summer, saying they had heard from an unspecified number of Canadians after the 2006 census who who were angry with the intrusiveness of the long form.

The long-form scrap prompted Statistics Canada chief statistician Munir Sheikh to resign.

The Statistics Act has provisions for fines for those who refuse to fill out the census.

Earlier this year, the former leader of Saskatchewan's Green Party, Sandra Finley, was found guilty of not completing her census.

Finley, 61, was charged in 2008 under the Statistics Canada for refusing to fill out her 2006 census. Though she was given repeated warnings, Finley refused, in protest for Statistics Canada buying software from U.S. weapons manufacturer Lockheed Martin.

Finley argued the mandatory census violated her privacy rights -- an argument her lawyer lost in court.

A handful of others have also tried over the years to protest the mandatory census. All have been unsuccessful.