H4 expiring on sep27,2013 got H1B approved is there need for extension

My H4 will expire on 27Sep2013, H1 got approved with COS from1stoct2013.Do i need to apply H4 extension for 3 days…What are the consequences if H4 extension is not apply for 3 days.

As it is question of 3 days, you should be fine. However, you should still check w/ your H-1 attorney for long term implications.