Lindsay Lohan didn't mean to stiff her recently fired lawyer Shawn Holley -- she just forgot there was a six-figure debt. As you do.

TMZ is claiming the amount LiLo owes her long-suffering (and highly efficient) attorney is upwards of $150,000, but Lohan says she just had no idea she was in the red for that much. So she's now instructed her business manager to take care of it post-haste, and even promises she'll cut back on her own overspending to make sure Holley gets paid.

Since LiLo still owes Uncle Sam $130,000 in back taxes, that means no more trashtastic fur coats, cartons of cigarettes and flying to England to brush up on her groupie skills.

Allegedly, Lindsay is still struggling to get Holley back in her employ and Holley is still not interested. Sounds like La Lohan is stuck with her smarmy new lawyer -- even if she'd rather not be.

On the upside, his sketchy reputation means maybe he's willing to accept payment in Monopoly money and a few dozen Wanted concert T-shirts.