iferror to be used twise as part of an if statement

We don't need to see the actual live file, just a sample/simulation of it so we can see the sheets, data layout, and expected results.

Without that, there's a lot of guesswork and a lot of effort building a test environment to check and correct your formula.

In the absence of anything to work with, I’d say remove the IFERROR functions and check the different parts of the formula separately. For example, put each of the MATCH functions in separate cells and see if they return what you expect, value or error. Then check the INDEX with the values returned from the MATCH functions, again, value or error. Then you know what's going wrong and where. Once you've done that, you can build a composite formula.

Happy to do that but not build the test rig for it.

Your formula is equivalent to:
=IFERROR(IF($G$2="Company",IF(AND(P$6>=$V$2,P$6<=$Y$2),(INDEX(Sheet1!$S$13:$CP$52436,MATCH(Sheet1!$B160,Sheet1!$C$13:$C$52436,0),MATCH(Sheet1!P$5,Sheet1!$S$2:$CP$2,0))*1000/P66),"Here you got false"),IFERROR((P178*1000)/(P126-P81),"")),"")


In other words in IF(AND(P$6>=$V$2,P$6<=$Y$2) you have only true part and no false part. But if AND(P$6>=$V$2,P$6<=$Y$2) is not met then IF returns FALSE. And FALSE is not an error, so is ignored by IFERROR and final result is returned as FALSE

Im'not sure if you noted my answer above. I think FALSE comes from other part of formula than you think.
If yes, you have seen - then I'll support TMS suggestion : spend some 10 minutes preparing a workbook free of any confidentional data (names converted to BRown, Black, Blue, companies to alpha Co, Beta Co etc. and show expected results

just:

Formula:

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Thanks for kind words :D and for a reputation point as well as for marking thread solved.
Have a good day.
If I fall into problems with deeply nested nested formulas I usually try to copy the formula (editing a formula bar) into another cell (or cells if outermost function has a number of arguments and remove this outermost function . Then repeat this approach with next level nested .