X12 837: Empty Box 5 (Tax Identifier Number) in certain scenario

[mtan-dev-work]

Question:
If an institutional 837 claim was submitted with separate billing-provider data (Box 1) and pay-to data (Box 2) and the pay-to TIN was no specified, is it expected for Box 5 to be blank ?

From the logic (https://github.com/bvanfleet/X12.NET/blob/master/src/X12.Hipaa/Claims/Claim.cs#L316-L330), I can see the precedence and why the output for Box 5 is blank. However, can the TaxId be copied from the billing-provider (Box 1) instead or is that against some requirements ?

Additionally, from X12.Hipaa.Claims, claim.PayToProvider.TaxId (Provider) is a private member.