As this NBO flag change will likely take some time to implement, might I suggest that, in the meantime, to encourage the dealers to do their claims correctly you begin reversing NBO claims that have the incorrect codes. This will force the dealers to re-submit the claims with the correct codes and provide the paperwork required by AAT so that MST is reimbursed. If the paperwork is not forthcoming then the claim is simply not approved or again reversed.