If your party was deregistered because you did not complete your annual registration confirmation, then you must continue with your party's reporting obligations until the end of your party's financial year.
If you have voluntarily deregistered your party, then it depends on your party's income and expenditure for its previous financial year:
if both your income and your expenditure were under £25,000, you must continue with your reporting obligations until the end of your party's financial year
if either your income or expenditure was over £25,000, you must continue with your reporting obligations until the end of your party's next financial year