Ok here's the deal people.  This is the REAL tab to this song.
The other tabs labeled "For Once In My Life" are simply imposters encouraging capo usage
and even raising the capo to accommodate a key change (WTF???).
Look I care about you guitar playing people of the world so I took it upon myself to
transcribe a great rendition of this song.
The version here is true to the original but to give credit where credit is due
I got the chords from the guitar player on the @NathanielTao cover
which you can feel free to look up on Youtube.  It's a great cover and will help you 
learn this song.

It seems challenging but you've got to think of it as more of a jazz chord progression
and not a pop song...though it is a pop song, it draws from jazz quite a bit.

Just so you know a Gm(M7)= G-Bb-D-F#...a G chord with a minor 3rd but a major 7th.

For Once In My Life  - Stevie Wonder
F                                           F#dim  Gm       Gm(M7)    Gm7-M7