I used the youtube video to tab this out as best I could.
A few youtube tutorial vids found with users screaming
out for a tab (including myself!) so here is my interpretation.

Tuning:
Open D

D (high E string)
A
F#
G
A
D (low E String)


1st Verse:
Now and then I think of when we were together
Like when you said you felt so happy you could die

|--------|---0---0----0----0---|
|-0------|--0---0----0----0----|
|-8------|-8---7---------7-----|
|--------|----------9----------|       x  2
|--------|---------------------|
|-9------|-9-------------------|


I told myself you were right for me, but felt so lonely in your company
But that was love and it's an ache I still remember

|--------|---------|--------|------|
|-0------|-0-------|-0------|-0----|
|-8------|-7-------|-5------|-7----|
|--------|---------|--------|------|       x  2
|--------|---------|--------|------|
|-9------|-7-------|-5------|-7----|


Chorus:
But you didn't have to cut me off, make it out like it never happened and that we were nothing
And I don't even need your love, but you treat me like a stranger and it feels so rough

|--------|-------|--------|---------|---------|-------|--------|--------|
|---0----|-------|---0----|------0--|---0-----|-------|---0----|--------|
|--0-----|-------|--0-----|-----0---|--0------|-------|--0-----|--------|
|-4------|-------|-4------|----2----|-4-------|-------|-2------|--------|
|-2------|-------|-2------|----0----|---------|-------|-0------|--------|
|--------|-------|--------|---------|-5-------|-------|--------|--------|
(let ring)

No, you didn't have to stoop so low, have your friends collect your records and then 
change your number
I guess that I don't need that though, Now you're just somebody that I used to know

|--------|-------|--------|---------|---------|-------|---------|--------|
|---0---0|---0--0|---0--0-|---0---0-|---0--0--|--0--0-|---0--0--|--------|
|--0---0-|--0--0-|--0--0--|--0---0--|--0--0---|-0--0--|--0--0---|--------|
|-4---4--|-4--4--|-4--4---|-4---2---|-4--4----|4--4---|-2--2----|-2------|
|-2------|-------|-2------|-----0---|---------|-------|-0-------|-0------|
|--------|-------|--------|---------|-5-------|-------|---------|--------|

break
|---0---0----0----0---|
|--0---0----0----0----|
|-8---7---------7-----|
|----------9----------|
|---------------------|
|-9-------------------|

2nd verse
Now and then I think of all the times you screwed me over
But had me believing it was always something that I'd done

|--------|---0---0----0----0---|
|-0------|--0---0----0----0----|
|-8------|-8---7---------7-----|
|--------|----------9----------|       x  2
|--------|---------------------|
|-9------|-9-------------------|

But I don't wanna live that way, Reading into every word you say
You said that you could let it go and I wouldn't catch you hung up on somebody that you 
used to know

|--------|---------|--------|------|
|-0------|-0-------|-0------|-0----|
|-8------|-7-------|-5------|-7----|
|--------|---------|--------|------|       x  2
|--------|---------|--------|------|
|-9------|-7-------|-5------|-7----|

Chorus:
But you didn't have to cut me off, make it out like it never happened and that we were nothing
And I don't wanna live that way, but you treat me like a stranger and it feels so rough

|--------|-------|--------|---------|---------|-------|--------|--------|
|---0----|-------|---0----|------0--|---0-----|-------|---0----|--------|
|--0-----|-------|--0-----|-----0---|--0------|-------|--0-----|--------|
|-4------|-------|-4------|----2----|-4-------|-------|-2------|--------|
|-2------|-------|-2------|----0----|---------|-------|-0------|--------|
|--------|-------|--------|---------|-5-------|-------|--------|--------|
(let ring)

No, you didn't have to stoop so low, have your friends collect your records and then 
change your number
I guess that I don't need that though, Now you're just somebody that I used to know

|--------|-------|--------|---------|---------|-------|---------|--------|
|---0---0|---0--0|---0--0-|---0---0-|---0--0--|--0--0-|---0--0--|--------|
|--0---0-|--0--0-|--0--0--|--0---0--|--0--0---|-0--0--|--0--0---|--------|
|-4---4--|-4--4--|-4--4---|-4---2---|-4--4----|4--4---|-2--2----|-2------|
|-2------|-------|-2------|-----0---|---------|-------|-0-------|-0------|
|--------|-------|--------|---------|-5-------|-------|---------|--------|

Somebody....Somebody that I used to know
Now you're just somebody that I used to know
Somebody oh, somebody that I used to know
Now you're just somebody that I used to know

|---0----0----0----0----|          |---0----0----0----0----|         |
|--0-0--0-0--0-0--0-0---|          |--0-0--0-0--0-0--0-0---|         |
|-8---7----------7------|  x 2     |-8----7----5----7------|  x 2    |    Play this twice overall
|-----------9-----------|          |-----------------------|         |     and play the (7) on the
|-----------------------|          |-----------------------|         |     last of each run
|-9---------------------|          |-5--------------(7)----|         |

Last Chorus:
But you didn't have to cut me off, make it out like it never happened and that we were nothing
And I don't even need your love, but you treat me like a stranger and it feels so rough

|--------|
|-0------| vocals continue chord progression, but could be played as above.
|-8------|
|--------|
|--------|
|-9------|


No, you didn't have to stoop so low, have your friends collect your records and then 
change your number
I guess that I don't need that though, Now you're just somebody that I used to know

|--------|-------|--------|---------|---------|-------|---------|--------|
|---0---0|---0--0|---0--0-|---0---0-|---0--0--|--0--0-|---0--0--|--------|
|--0---0-|--0--0-|--0--0--|--0---0--|--0--0---|-0--0--|--0--0---|--------|
|-4---4--|-4--4--|-4--4---|-4---2---|-4--4----|4--4---|-2--2----|-2------|
|-2------|-------|-2------|-----0---|---------|-------|-0-------|-0------|
|--------|-------|--------|---------|-5-------|-------|---------|--------|


Somebody....Somebody that I used to know
Now you're just somebody that I used to know
Somebody oh, somebody that I used to know
Now you're just somebody that I used to know

|---0----0----0----0----|          |---0----0----0----0----|         |
|--0-0--0-0--0-0--0-0---|          |--0-0--0-0--0-0--0-0---|         |
|-8---7----------7------|  x 2     |-8----7----5----7------|  x 2    |    Play this twice overall
|-----------9-----------|          |-----------------------|         |     and play the (7) on the
|-----------------------|          |-----------------------|         |     last of each run
|-9---------------------|          |-5--------------(7)----|         |

End on:
|-0-|
|-0-|
|-8-|
|---|
|---|
|-9-|