happy new year all. is it possible to not auto generate negative rev arrangement/item/plan for credit memos?

nope, it is part of your transaction - that is it follows the settings of the item

only way I could think of achieving this would be to create duplicate items with the "direct revenue posting" option ticked (e.g. you have items with external IDs ABC and ABC_CRED). If you're loading a credit note, pick the duplicate item, otherwise pick the normal one. Depends on how big your item list is / what you're doing with inventory, etc.

thanks much!!

Does this just happen automatically or is there a setting? I have been having to create the rev arrangements manually by cliicking the update rev arrangements button

you need to updated your Advanced revenue Management setting under Setup > Accounting Preferences > in General tab scroll down to ARM section and switch from Manual to Automatic under Revenue Arrangement Update Frequency

Thanks!