9/6 8:43 AM PT -- Hunter Biden followed through with his plans to switch up and plead guilty in his tax evasion trial. The judge ticked off each of the 9 charges against Hunter in court, with President Joe Biden's son repeatedly saying "guilty" to each one.

The judge scheduled sentencing for December 16 ... and in the meantime, Hunter will remain free on bond.

Hunter Biden is planning to enter a guilty plea in his controversial tax evasion trial ... the first son's attorneys have revealed.

President Joe Biden's son arrived at a Los Angeles courthouse alongside his wife, Melissa Cohen Biden, on Thursday ... but Hunter's trial is unlikely to last long given his decision to change his plea.

His attorney, Abbe Lowell, shared Hunter's decision to plead guilty in the federal courtroom, noting ... "Mr. Biden intends to change his plea this morning."

Prior to this surprise announcement, Hunter's defense and the prosecution planned to kick off the jury selection process ... which has since been paused.

The prez's younger son -- who was convicted on 3 federal firearms-related felony charges back in June after confessing to illegally owning a gun while he was an active drug user -- faced 9 federal charges heading into Thursday's trial ... after he allegedly failed to to pay $1.4 million in taxes between 2016 and 2019.

He was facing a 17-year prison sentence if convicted on all 9 charges ... which would've been in addition to the 25 years he potentially faces in his gun case. HB is set to be sentenced for the gun drama in November.

We're sure more developments are to come ... so, stay tuned!!!