It is a fatal error (1147) if the required id argument is not a number. Characters up to and including an equals sign in id are ignored without complaint.

If id is not a non-zero number less than 64K, it is ignored with a warning (LNK4220). The text for warning LNK4220 reads as if LINK reverts to a default. This is not strictly true. The invalid id is just ignored. If an earlier /tlbid set a valid id, then the earlier setting persists.

The /tlbid option is for the command line only. It is not valid as a directive in an object file.