Difference between 接受 and 接收
接受(accept) ≠ 接收(receive)


  接受 means agreeing to something
  
  接收 means getting something


I have made some amendments to the six sentences (in brackets) for clearer understanding of the meaning:


我接受(了)邀请。I accepted the invitation.
他将接受口试。He will be (accepting) an oral test.*
他拒绝接受治疗。 He refused (to accept) treatment.
我接收了邀请(函)。I received the invitation (letter).
部队未接收他。The military has yet to (receive) him.*
他接收了礼物。He received the gift.


接受 can be used in an abstract manner (邀请，口试，治疗) but 接收 has to be something physical (邀请函，他，礼物). Therefore, they can't be interchanged.

&#42; These statements may sound unnatural to native English speakers. Gloss translation is provided to give the precise meaning of 接收 and 接受, and to avoid causing confusion to learners of the Chinese language.