A contested test case about insurance payouts for small businesses who were unable to trade owing to lockdown is due before the Supreme Court today (Monday).
Many firms made claims on their business interruption insurance after closing or having faced significant losses.
But insurers disputed the claims, arguing policies were never meant to cover such unprecedented restrictions.
Supreme Court judges will make a final judgement after the hearing, which is expected to last four days.
The issue will have had implications for 370,000 – mostly small – businesses, and involves potential payouts of £1.2 billion, according to the BBC.
High Court judges earlier found mostly in favour of insurers having to pay out to policyholders regarding a selection of policy types.
Some of these decisions are now being appealed against at the Supreme Court.
The High Court looked at 21 policy types as part of a test case, and rulings on 13 have been appealed against.
These will be discussed in complex legal arguments at the Supreme Court this week.