The ETP corpus encompasses inscriptions that were composed to convey a linguistic message. An exception to this criterion is made in the case of abecedaria, which are too important for the history and development of writing in Etruria to be excluded from the database.

The ETP corpus does not include inscriptions consisting of one or two letters, or fragmentary inscriptions consisting of one, two, or three letters, particularly in cases where it is not possible to determine the word-form that was intended. The ETP corpus does not include letters incised on ceramic and intended as potters' or dealers' marks, and it does not include letters incised on terracotta roof and cover tiles, which may have functioned to indicate the location or position of the tiles.