You can settle early if every party agrees and is ready. That includes the banks, so check your bank is ready before you agree to bring the date forward.
You can also agree to delay settlement. Put the agreement in writing as a simple variation of contract signed by the buyer and the seller. The real estate agent can prepare one.
Without a signed variation, a settlement completed more than three business days after the due date can expose the delaying party to penalty interest. The three business days are a threshold rather than a free period, so once they pass the interest is calculated from the settlement date itself.
