Return date at which a sum was reached

use a helper column (Col. C). In C2
=IF(A2<$F$3,"",SUM(C1,B2))

copy down

then use
=INDEX(A:A,MATCH(F2,C:C)+1)

Based on your last post in this thread, its apparent that you are satisfied with the solution(s) you've received and have solved your question, but you haven't marked your thread as "SOLVED". I will do it for you this time.

In future, to mark your thread as Solved, you can do the following -
Select Thread Tools-> Mark thread as Solved.

Incase your issue is not solved, you can undo it as follows -
Select Thread Tools-> Mark thread as Unsolved.

Also, since you are relatively new to the forum, i would like to inform you that you can thank those who have helped you by clicking the small star icon located in the lower left corner of the post which helped you. This adds to the reputation of the person who has taken the time to help you.

If you want a single formula...

This array formula** entered in F4:

=INDEX(A551:INDEX(A2:A551,MATCH(F3,A2:A551,0)),MATCH(TRUE,SUBTOTAL(9,OFFSET(B2,MATCH(F3,A2:A551,0)-1,,ROW(INDIRECT("1:"&COUNT(A551:INDEX(A2:A551,MATCH(F3,A2:A551,0)))))))>=F2,0))

** array formulas need to be entered using the key
combination of CTRL,SHIFT,ENTER (not just ENTER).
Hold down both the CTRL key and the SHIFT key
then hit ENTER.

Format as Date

It makes things a bit more complex but it can be done.

Create this defined named formula:

Goto the Formulas tab>Define Name
Name: Dates
Refers to: =$A$2:INDEX($A:$A,MATCH(1E+100,$A:$A))
OK

Then, this array formula** entered in F4:

=INDEX(INDEX(Dates,MATCH(1E+100,Dates)):INDEX(Dates,MATCH(F3,Dates,0)),MATCH(TRUE,SUBTOTAL(9,OFFSET(B2,MATCH(F3,Dates,0)-1,,ROW(INDIRECT("1:"&COUNT(INDEX(Dates,MATCH(1E+100,Dates)):INDEX(Dates,MATCH(F3,Dates,0)))))))>=F2,0))

** array formulas need to be entered using the key
combination of CTRL,SHIFT,ENTER (not just ENTER).
Hold down both the CTRL key and the SHIFT key
then hit ENTER.

Please refresh my memory.

Just looking at your file I can't follow what you're wanting to do. The manual result that I get is not even close to the formula result.

Hi, I want to thank the OP mihigh for this post as well as Ace_XL for providing a great solution. I am quite new to Excel formulas and so there is still a few things within the formula that I don't understand, but I'm usually a quick learner.

I am using this exact solution in my spreadsheet with my own cell references as for the most part it is does exactly what I need and what I expect.

If the sum has not yet been reached within the data, it returns the date '0 January 1900'. Is there a way I can either, get it to display nothing if the sum is not reached, or perhaps some custom text?

Total noob here Apologies if this is a basic things and I just don't have the information yet.