With certain exceptions, VAT returns resulting to pay cannot be postponed and must be paid within the corresponding voluntary period, which deadline is:
1. For quarterly VAT returns (small companies), up to the 20th of the month following the quarter to declare.
2. For monthly VAT returns (companies with a turnover exceeding 6 million Euros), up to the 30th of the month following the one to declare.
Source ivaconsulta