Date range formula showing with VALUE or 0 result

The only thing that is sticking out to me is this part:

=SUMIFS(I2:I9999,G2:G9999,">"&A395,G2:G9999,"<w"&B395)

I recommend uploading a small representative sample of your data along with the desired results (which you can enter manually) based on that data.

To upload an Excel workbook, follow these steps:
1) Click on "Go Advanced"
2) Click on "Manage Attachments"
3) Click on "Choose File"
4) Choose your file and click on "Open"
5) Click on "Upload"
6) Click on "Close this window"

Thank you, I have added a sample of the data set.

Deleting the w in your formula from post #1 (and putting the dates into cells A395 and B395), gives me -420.89

See attachment.

That being said, if you're looking for the total for the month of January, you either want to use "<=" the last day of the month or "<" the first day of the next month.

I just noticed that most of the dates are not being recognized as actual dates.

To fix this, highlight column G > Data > Text to Columns > Finish

I have copied and pasted the formula directly off the workbook you attached into the one I sent and it is still showing 0. Would it be something to do with my excel or the way the dates are formatted?
Attachment 645396

Fantastic, you are an absolute star!!
It's working perfectly now.
Thank you