Query about Offer letter from US Employer

[hari1177]

Hi,

I got H1B approval by 1st Oct.
And employer Offer dates also same.
And I am going to attend the interview in Month of Dec and planning to fly end of Jan and will join there 1st week of Feb.

Do we need any letter from US employer that stating that, we can join in 1st week of Feb again?
because already they submitted a offer letter in the US, right?, so do we need to take new offer letter OR any letter with new dated?

Please answer to this ASAP.