Hey @Linda
If you remove an accrual policy, the main issue is the entitlement will no longer be granted to the employee resulting in negative balances if absences have been taken. To clear up any confusion, the removal of an accrual policy does not have any effect on absence periods and they will remain in the absence type. Therefore the past flexitime would not be removed from the Absence Calendar. The only time the absences will be removed is if the absence type is deleted.
In order to fix negative balances for your employees, an accrual policy with their entitlement needs to be assigned (For example 10 days per entitlement period). So as you mentioned, you currently have an accrual policy of 0 days assigned to employees, however as they have taken absences using the absence type, they are now in a negative.
You can assign an accrual policy with their set entitlement and this will now balance out the negative number (so long as they have not taken more days than they are entitled to). If you run into difficulties when doing this, please let me know and I can guide further.
Best regards,
Conor