It's time for Screen Actors Guild members to start paying close attention to their mailboxes.

On Friday, three days after the Academy mailed out Oscar ballots, SAG sent postcards to nearly 100,000 of its members. And for members who want to have a say in this year's SAG Awards, those postcards are essential.

The cards, which are being sent to every member of the guild eligible to vote, contain ballot instructions that will enable members to cast their ballots online for the 18th SAG Awards.

Paper ballots will not be mailed to members unless they request them by calling a toll-free number, (877) 610-8637, before five p.m. on Monday, January 16.

SAG has been encouraging its members to vote online for the last seven years, but 2010 was the first time that it mailed a postcard to advise members that paper ballots would be available by request only.

Although the change was publicized at the time in an October 2010 press release and a fall issue of Screen Actor magazine, many members contacted TheWrap to complain that they didn't notice or had misplaced their postcards, and were having a hard time voting.

The process remains in place this year, with members needing a PIN number included on the postcards to vote online.

Last year's cards also contained codes good for free downloads of nominated movies, and for coupons that provided free admission to movie theaters.

SAG is by far the largest Hollywood guild, with around 120,000 members. Only members whose November dues were paid by December 16 are eligible to vote, which reduces the number of potential voters to between 90,000 and 100,000.

SAG has been honored by the Environmental Media Association for its green practices.