JERMAINE JACKSON may be going to jail soon.

JERMAINE JACKSON: Pay child support or go directly to jail.

Jermaine is falling farther and farther behind.... He’s required to pay baby mama Alejandra Jackson $3K a month for 13-year-old Jermajesty and 17-year-old Jaafar … but the mailbox has been empty for months.

Court docs obtained by TMZ show … of the $12K that he owes in back payments … he’s only coughed up a measly 85 bucks.

The L.A. County Child Support Services Dept. has filed papers asking a judge to hold Jermaine in contempt ... which could put him behind bars for 20 days.

BTW, this isn’t the first time Jermaine has slacked off.  He belatedly paid $80,000 back in March 2011 … and anted up another $33K in back support this past May.  He's also had his wages garnished.

If the current case goes before a judge, Jermaine is gonna have a hard time explaining how he dropped $160K last month for a Ferrari.