In the IBMF tagset, it has been found useful for disambiguation purposes to refine the proper noun class into subclasses. It can be noted that some of these classes bear gender/number information.
| Tag | Meaning | Examples |
| XFAMIL | family name | Smith, Dupont |
| XPAYFP | country name, fem.pl. | (les) Seychelles |
| XPAYFS | country name, fem.sing. | (la) France |
| XPAYFP | country name, masc.pl. | (les) U.S.A. |
| XPAYFP | country name, masc.sing. | (le) Danemark |
| XPREF | christian name, fem. | Mary, Marie |
| XPREM | christian name, masc. | John, Jean |
| XSOC | company name | Olivetti, IBM |
| XVILLE | city name | Paris, Pise |