The more common forms (modelos) that need to be filed for an SL are:
Most quarterly forms are due on the 20th of the month following the quarter. However, if you owe money (potentially in Form 111, 115, 303, or 200), then you will need to file 5 days earlier if you want the Spanish tax office to take the payment directly from your bank account. Most annual forms are due at the end of January.
Other tax forms include: