Transfer of funds from NRI to NRI spouce's NRE account

Transferred fund from abroad  in NRE account is not taxable, it's tax free .

Do we need to do any documentation for this . Since we both are NRIs and funds are transferred from Dubai to spouc's NRE account . no documents are needed.

Please clarify 

Sir,

my question is if both are NRIs and spouce is transferring money from Dubai to the NRE account of his/ her NRI spouce,

It will be no doubt tax free but since the transaction is taking place overseas and money is transferred to Indian NRE account , is there documentation needed between the husband -wife for the purpose of income tax.

In short how will Income Tax authorities treat this as  if there is no written deed between husband and wife? 

Regards.

Kindly give an elaborate reply for easy understanding.