Late submissions accrue penalty points rather than an immediate fine. You get a point per missed deadline, and only when you reach the threshold for your filing frequency does a fixed financial penalty apply. Points then expire after a period of consistent on-time filing, so a single slip in an otherwise clean record is not the disaster it might feel like. Late payment is treated separately and charged as interest plus penalties that escalate the longer the balance is outstanding, which in practice makes paying late more expensive than filing late. The practical implication is worth internalising: always submit, even if the figures are rough, because a provisional update you can correct later costs nothing and a missed one costs a point.