Rule reminder
Causal conjunctions operate across a register spectrum: INFORMAL: perché, visto che, dato che. NEUTRAL-FORMAL: siccome, visto che, dal momento che, dato che. FORMAL: poiché, in quanto. VERY FORMAL/LITERARY: giacché, poiché, participio assoluto, causal gerund. The same cause can be expressed at different registers. Choosing the right register is essential in professional and academic Italian.
You are writing a formal legal notice. Which structure is most appropriate for 'since the deadline has passed'?