use fuel_types::{ContractId, AssetId, Address};
pub struct TransferOut {
    pub contract_id: ContractId,
    pub to: Address,
    pub amount: u64,
    pub asset_id: AssetId,
    pub pc: u64,
    pub is: u64,

You can handle functions that produce a TransferOut receipt type by adding a parameter with the type abi::TransferOut.

fn handle_transferout(transfer_out: abi::TransferOut) {
  // handle the transfer out