Charlie Sheen and Lindsay Lohan are suddenly, pals.

In fact, he recently sent Lohan a $100,000 check to cover the actress' six-figure tax bill.

Charlie and Lindsay became close pals while on the set of "Scary Movie 5" back in September.

At one point, Lindsay mentioned her ongoing tax problems.

Sources say Charlie offered to cut her a check then, but Lindsay refused.

Last week, Lindsay's biz manager received a check from Charlie for $100,000.

According to TMZ, Lindsay was blown away by Charlie's generosity and applied the money to her outstanding tax bill.

She owed Uncle Sam $233,904 in unpaid taxes for 2009 and 2010.

Sheesh...he could have bought so many drugs with that.  Such a nice guy.

-AJ