Q: Multiple Nested IF formula receive Error: Syntax error. Extra ',' I'm trying to write a multiple nested if formula but keep receiving the following error. 
Error: Syntax error. Extra ','
IF((TODAY() > CloseDate && TEXT(StageName)='Donation Likely'),TRUE),   
IF((TODAY() > CloseDate && TEXT(StageName)='Donation Prospecting'),TRUE),
IF((TEXT(StageName) <> 'Donation Likely'||TEXT( StageName ) <> 'Donation 
Prospecting'|| TODAY() < CloseDate,FALSE)


A: You are missing some parts. Try this and pay attention to the ??? which is the false part of the last if
IF(
   (TODAY() > CloseDate && TEXT(StageName)='Donation Likely'),
   TRUE,   
     IF(
         (TODAY() > CloseDate && TEXT(StageName)='Donation Prospecting'),
         TRUE,
            IF(
             TEXT(StageName) <> 'Donation Likely'||TEXT( StageName ) <> 'Donation 
             Prospecting'|| TODAY() < CloseDate,
             FALSE,
             ????
           )
     )
)

You are basically doing (from what I gather from your attempt):
IF(
   EVAL,
   TRUEPART,
   FALSEPART = IF(EVAL,TRUEPART, FALSEPART = IF(EVAL,TRUEPART,FALSEPART)
)

Every IF statement has an Eval, TruePart, and FalsePart. When nesting you can get lost easily. 
Note I did not evaluate to see if there was a better way of doing what you are trying to do so Optimization is still possible and may be posted as an answer by another SFSE team member :0

A: Don't you think this formula can be simplified?
In first two IF CloseDate is common only difference is the StageName so, we can combine both conditions as:
IF(
      (
         TODAY() > CloseDate 
         && (TEXT(StageName)='Donation Likely' || 
             TEXT(StageName) = 'Donation Prospecting')
      ), 
      TRUE, 
      FALSE
)

In all other conditions you just want FALSE even the CloseDate > Today() regardless of stage, formula will evaluate to false.
Note: It is little difficult initially but make sure brackets are closed properly.
