This paper presents the results of a corpus-based study on the contribution of Spanish aspectual auxiliary verbs to the factual interpretation of the predicates they modify and with which they constitute the verb complex (a verb periphrasis, VP). The study was carried out as part of a project that, based on linguistic knowledge, aimed at automatizing the annotation of the factual status of texts in this language. We analyzed 674 sentences in European Spanish extracted from four corpora, where 28 VPs were represented, considering only indicative tenses. Interestingly, the results show that, although one of the most important aspects that affects the factual interpretation in sentences with VPs is the verb tense of the auxiliary, in a few VPs, the type of auxiliary changes the factual value expected for the VP taking into account the tense used. Finally, based on the data under analysis, the study concludes that it is feasible to state general rules to automate the annotation of factuality for most of the aspectual VPs studied.