Spanish Perfect Future Subjunctive
Just like the Spanish Future subjunctive, the Spanish Perfect Future subjunctive is a tense that is rarely used nowadays. You won't find this tense in everyday conversation or even in a formal conversation. You may come across this tense in some legal documents or old literary contexts.
Serán rechazadas las reclamaciones cuando, en los tres meses anteriores a estas, se hubiere presentado y respondido una reclamación similar.
Claims will be rejected if, in the three months prior to these, a similar claim has been submitted and responded to.
This tense conjugation is rarely taught when you learn Spanish as a foreign language as it is so rare nowadays and not practical at all. You can use the present perfect subjunctive or the pluperfect subjunctive instead without changing the meaning.
You conjugate in the Spanish Perfect Future subjunctive by adding the verb haber as follows and the past participle of the main verb:
hubiere, hubieres, hubiere, hubiéremos, hubiereis, hubieren ( + past participle of main verb)