Accounts filed (dormant accounts excluded)
Turnover, profit, net assets, cash or headcount changing by a quarter or more, losses, net liabilities
A new director joins the board
A director leaves the board
A person with significant control is added or removed
New shares issued, or share capital restructured
Secured lending registered, or a charge satisfied
Strike-off notices, dissolution, strike-off suspended
Only when the office moves to a different postcode area
Annual confirmations that report a change (routine ones never alert)
Trading accounts filed after dormant accounts
Liquidation, administration and other insolvency filings
Routine filings (confirmation statements without changes, minor address changes, dormant accounts) never alert.