The error was actually just a simple syntax issue - the placement of your parentheses - here is the correct:
=IF(H4=1, "CORRECT", IF(H4=2, "CORRECT", IF(H4=3, "CORRECT")))
I also fixed it on your spreadsheet.
Every if statement must have 3 parts essentially, so if(this, then this, else this) so when nesting, the else this part of the formula is the next condition..
=IF(h4=1, "CORRECT", IF(h4=2, "CORRECT", IF(h4=3, "CORRECT", IF(h4=4, "CORRECT"))))
Answer from Aurielle Perlmann on Stack OverflowHelp with multiple IF(AND) statements, Google Sheets! - Google Docs Editors Community
if statement - Multiple nested if blocks in google spreadsheets formulas - Stack Overflow
How do I use multiple IF statements in a cell for two different conditions? - Google Docs Editors Community
google sheets - Multiple IF statements between number ranges - Stack Overflow
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UPDATE: FIXED IT!! Thank you everyone!!
I need to create a formula that tells me IF the container ID's 8th and 9th character (in this case "01") contains a certain value then the output would be a specific number. My initial solution was to do:
=ArrayFormula(right(split(B9,"ML"),4))
in column C to isolate the last 4 digits, since I can't figure out how to isolate ONLY the 8th and 9th characters. But I am still stuck on how to tell it IF "01" then 6, IF "02" then 10, and so on.
How do I create several IF statements in one formula?
https://preview.redd.it/ztsqbqnjulu71.png?width=290&format=png&auto=webp&s=37e13e777e119c6d376a98b4eff3b8b917b9d68b
The error was actually just a simple syntax issue - the placement of your parentheses - here is the correct:
=IF(H4=1, "CORRECT", IF(H4=2, "CORRECT", IF(H4=3, "CORRECT")))
I also fixed it on your spreadsheet.
Every if statement must have 3 parts essentially, so if(this, then this, else this) so when nesting, the else this part of the formula is the next condition..
=IF(h4=1, "CORRECT", IF(h4=2, "CORRECT", IF(h4=3, "CORRECT", IF(h4=4, "CORRECT"))))
Short answer
Instead of nesting multiple IFs, try to use a formula that doesn't require that. Considering the example provided, one alternative is the following:
=IF(AND(h1>=1,h4<=4),"CORRECT")
Explanation
If it's possible, avoid function nesting as it could make a formula harder to read and debug.
It's a little tricky because of the nested IFs but here is my answer (confirmed in Google Spreadsheets):
=IF(AND(A2>=0, A2<500), "Less than 500",
IF(AND(A2>=500, A2<1000), "Between 500 and 1000",
IF(AND(A2>=1000, A2<1500), "Between 1000 and 1500",
IF(AND(A2>=1500, A2<2000), "Between 1500 and 2000", "Undefined"))))
I suggest using vlookup function to get the nearest match.
Step 1
Prepare data range and name it: 'numberRange':

Select the range. Go to menu: Data → Named ranges... → define the new named range.
Step 2
Use this simple formula:
=VLOOKUP(A2,numberRange,2)

This way you can ommit errors, and easily correct the result.