My first tab so let me know what you think.

Capo 4

G  D  Em  Cadd9
  E- (022100@1) 3  2  0    0
  B- (x2444x@1) 0  3  0    3
  G- (320003@1) 0  2  0    0
  D- (xx0232@1) 0  0  2    2
  A- (x02220@1) 2  x  2    3
  E- (022100@1) 3  x  0    x

Sometimes the Cadd9 sounds better with the high E string playing a 3 instead of 0. 
Just something I found.

Intro: G Cadd9 G Cadd9

G (320003@1)         D (xx0232@1)                      Em (022000@1)              Cadd9I (x32030@1)can't explain, what goes on in my brain,   But it's beautiful and scary baby 
G (320003@1)           D (xx0232@1)                Em (022000@1)            Cadd9I (x32030@1)don't know why I can't quite define ,   How my heart beats when I'm with you 
          G (320003@1)                                                  Cadd9But (x32030@1)it's somethin' like summer,    And somethin' like Saturday night 
                                                 EmSomethin' (022000@1)like getting drunk for the very first time 
                           Cadd9 (x32030@1)             DFree (xx0232@1)fall, cannon ball ,   Into the river no clothes at all 
          G (320003@1)                                            Cadd9And (x32030@1)it's somethin' like sunshine hearing my name on your lips 
                                              EmLike (022000@1)a song and goes a little something like this

WOAH OH 
                    Cadd9I (x32030@1)don't know what it is for sure 
          Cadd9 (x32030@1)                         D (xx0232@1)                 G (320003@1)    D (xx0232@1)   Em (022000@1)   Cadd9But (x32030@1)this somethin' like somethin' feels nothin' like nothin' before

G (320003@1)                 D (xx0232@1)                      Em (022000@1)          Cadd9I (x32030@1)would be a millionaire if I could sell the air ,  That I walk on when I'm near you baby 
G (320003@1)                   D (xx0232@1)                          EmI, (022000@1)I wouldnt save a dime,    I'd spend it all on time 
    Cadd9Everyday (x32030@1)the rest of my life would be 
G (320003@1)                                           Cadd9Somethin' (x32030@1)like summer somethin' like Saturday night 
                                                 EmSomethin' (022000@1)like getting drunk for the very first time 
                          Cadd9 (x32030@1)              DFree (xx0232@1)fall, cannon ball ,   Into the river no clothes at all 
           G (320003@1)                                           Cadd9And (x32030@1)it's somethin' like sunshine hearing my name on your lips 
                                                 EmLike (022000@1)a song and it goes a little something like this

WOAH OH 
                    Cadd9I (x32030@1)don't know what it is for sure 
          Cadd9 (x32030@1)                        D (xx0232@1)                  G (320003@1)    D (xx0232@1)  Em (022000@1)   Cadd9But (x32030@1)this somethin' like somethin' feels nothin' like nothin' before

G (320003@1)                  D (xx0232@1)                              EmNo (022000@1)we can't put a label on it ,   Not sure what we would call it 
       Cadd9But (x32030@1)it feels so good

G (320003@1)                                               Cadd9Somethin' (x32030@1)like summer and somethin' like Saturday night 
                                                EmSomethin' (022000@1)like getting drunk for the very first time 
                           Cadd9 (x32030@1)            DFree (xx0232@1)fall, cannon ball ,   Into the river no clothes at all 
       G (320003@1)                                          Cadd9It's (x32030@1)somethin like sunshine hearing my name on your lips 
                                                 EmLike (022000@1)a song and it goes a little somethin' like this

WOAH OH 
                    Cadd9I (x32030@1)don't know what it is for sure 
          Cadd9 (x32030@1)                        D (xx0232@1)                   G (320003@1)       Cadd9 (x32030@1) 
But this somethin' like somethin' feel nothin' like nothin' before
                    GLike (320003@1)nothing before 
         Cadd9 (x32030@1)                                            G (320003@1)      Cadd9 (x32030@1)  GThis (320003@1)somethin' like somethin' feels nothin' like nothin' before