Please don't SHOUT.

Use some of the details space to give some more details on precisely what you're asking.

Are you preparing LLC A's 1065?

Sorry about that.  Yes I am preparing the return for A.  B & C have losses and C's loss brings A's basis in C below zero .

Lacerte is not very robust when it comes to pass throughs to pass throughs. You'll need to compute the allowed loss yourself and manually limit it in the return. Keep a side spreadsheet of your computation and carryover.