A lawyer for the 26-year-old star appeared in court on Thursday on her behalf and entered not guilty pleas on two misdemeanour hit-and-run charges.
Bynes, whose next court hearing is scheduled for October 19, is alleged to have struck a car and then left the scene in separate crashes in April and August.
In the earlier incident, Bynes reportedly hit a BMW on a Los Angeles freeway and then drove off.
In the latter case, the What I Like About You actress was said to have left the scene of an accident without exchanging information with the other driver after a rear-end collision.
She could serve up to a year behind bars as each charge carries a maximum sentence of six months' imprisonment and a $1,000 fine.
Bynes also faces a Driving Under the Influence charge from April after she allegedly struck an LA County sheriff's cruiser in West Hollywood.
She pleaded not guilty in that case and has publicly contested the hit-and-run and DUI charges.
The star was recently dropped by her agent, publicist and entertainment lawyer after they were unable to get in touch with her for four weeks.