Here is One custom object name is target setting on that object distributor name(name. of distributor) field is present which is lookup to target setting object. (distributor(parent) & target setting(child)). so user have only permit to create only one record per year for user(distributor) otherwise show error(if user try to create another record with same distributor show error 'you can't create more than one record for + distributor name. in present year')

system admin can create only one record for per contact(lookup) if admin try to create another record with same contact then show error

Here is One custom object name is target setting on that object distributor name(name. of distributor) field is present which is lookup to target setting object. (distributor(parent) & target setting(child)). so user have only permit to create only one record per year for user(distributor) otherwise show error(if user try to create another record with same distributor show error 'you can't create more than one record for + distributor name. in present year')

system admin can create only one record for per contact(lookup) if admin try to create another record with same contact then show error