Prior to transferring a firearm to a non-licensee, a federally licensed firearms dealer is required to review the customer’s valid government issued identification document pursuant to 27 CFR §§ 478.11 and 478.124(c)(3)(i).
An expired government issued identification document cannot be used because it is no longer valid, but there is no requirement that the government issued identification document have an expiration date. Per Question 18a. on the ATF Form 4473, the identification expiration date is only required if it exists on the government issued identification document ("Expiration Date of Identification (if any)").
In this case, because the customer’s Non-Driver’s Identification does not have an expiration date, you should leave the space for the expiration date in Question 18.a. blank. FFLGuard recommend that you write "customer’s ID states ‘NONEXP’" in the space provided in Question 31 on the Form 4473 to prevent the ATF from mistakenly believing that you forgot to list the expiration date if the Form 4473 is reviewed during a compliance inspection.