Can I submit the OSS return retroactively?

OSS returns cannot be submitted retroactively; local VAT registrations are required.

No, OSS returns cannot be filed retroactively. Once you exceed the €10,000 threshold, you must pay VAT in the destination country. If you do not yet have an OSS registration, you need to apply for a local VAT number in each relevant country and file retroactive returns. Once your OSS registration is active, you can cancel these local registrations.