If you’ve chosen to delay making customs import declarations on non-controlled goods that you’ve brought in from the EU this year, you have to make a supplementary declaration within 175 days of your shipment arriving in GB. This means for imports you made in January 2021, your supplementary declaration will be due very soon.
This newsitem sets out the steps to follow to make sure that you’re ready to complete your declaration before your 175 days are up. You need to allow plenty of time to complete these actions.
Source HMRC