How to determined the Income from service??

Dear,
This depends on the method of Accountancy used by you i.e. whether Cash basis of Accountancy is being used or accural basis, in this regard, you should concern with the relevant laws for the purpose of applicability of the concerned jurisdiction.

You will recognize income when you receive cash in case of Cash basis ( i.e. Option 3 out of the options you provided) and in case of accural basis, you should recognize income when the event has been taken place or services have been rendered(i.e. option 2). However, if the services are still to be rendered & Accounting period has been ended during that time, then proportional basis will be more feasible, i.e. recognize only that portion of income, the services of which have been rendered (i.e. Option 1 , provided accural basis is being used).

Regards,

Desperado

suppose i'll take the proportionate basis, for the determination of income,

can i take the deferant method for other services,

or the same services to other client

To have a true and fair view in accounts, consistent practise shall be more viable to be applied in all areas of a particular business.

Your stated practise is not allowable in Laws, either recognize income proportionately or use other applicable method but you can not use partial method of your choice as per your convenience.

Best Regards,