Formula to Produce Totals Only

I know there is a simple to way to do this but can't seem to figure out. On the attached example, I have put in column N to total the amounts with the same invoice number in column I. What I normally do is then value column N and delete the cells that arrive at the invoice total which is tedious to say the least. Is there a formula that will give just the invoice totals? Also, this was an import from an accounting software (Quickbooks) and I've notice I get formatting issues when trying to work from the import, ie. if I put a formula in a blank column, it doesn't work so I copy the data into a new workbook which is annoying. Anyone know what causes this?

Thanks for your help

Try

=SUMIF(I:I,14738,L:L)

Will sum amounts for Inv # 14738

or

=SUMIF(I:I,O2,L:L)

O2 has invoice number

Thanks but the first solution sort of defeats the purpose as I would have to type in every new invoice number which would be far more time consuming than the semi manual way I'm doing it now. I tried the 2nd formula and all I get is zeros. Any other ideas?

Thanks again

Here is what I would do. I have attached a Spreadsheet with a Pivot Table. You can import the data on Sheet1. In order to do a Pivot Table,
each column has to have a header, or name. So in order to do that, I have the next Sheet called Pivot Table Data, show the information with headers.
Then you would simply right click on the Pivot Table and Refresh. It sums up all of the Invoices and puts them in numerical order. This is not a formula, but
what I would do for a fix.

I think this might be a little better than my first suggestion. You would import your Data on Sheet1, and then on the Filtered sheet, type your Invoice Number into Cell E1 and then your totals show up. The only problem is your data is text. It would have to be changed to numbers. I have attached a sheet. Hope this helps.