Kenneth Fisher gives us a quick post on bulk insertion against tables with identity columns:
TL;DR; BULK INSERT doesn’t have an easy way to specify a column list so the columns in the insert file must match the columns in the table unless you use a format file or a staging table.
As simple as they appear on the surface identity columns are fairly complicated things. BULK INSERT, on the other hand, is pretty complicated even on the surface (at least as far as I’m concerned). Because of this, the combination can get even worse. When you do an insert into a table that has an identity column you usually just ignore that column and it’s automatically filled in. However, that’s not true with BULK INSERT. Unless you use a format file, the number of columns (and their order) in the file has to match the table.
Read the whole thing.