I can't make a comment on pivot tables, but to get values from your child table is easy.

At the parent level, you can create a formula field, we can call it 'Total Roll Premium', with:

sum('Close or Roll Data'.'Roll Premium')

Then another formula to add the two fields together:

'Total Premium' + 'Total Roll Premium'

To filter reference links you would use the double brackets [ ].

If we use your pics from the original post then I guess it would look something like:

let t := this;
sum('Close or Roll Data'['Close or Roll' = t.'Trade Date'].'Roll Premium')

But first you need to gather the current record into a variable using the 'this' function.

Then you can you use that variable to reference any field in the parent record.

I can only see the column name 'Close or Roll', so I don't know if that is the full name. Please modify it with the full name if needed.

Why did you add the select command in there? We are using the reference link to get your data. With more info here is what it should look like:

let t := this;
sum('Close or Roll Data'['Close or Roll Date' = t.'Trade Date'].'Roll Premium')

For educational purposes we can troubleshoot the image.

The reason you are getting the error is because  you don't have a reference field called 'Closed-Roll Data' in your table 'Closed-Roll Data'.

Rick Castellini said:
The "Trade Date" in my Trade Details table  (and in the "Income by Day" view I'm trying to create) is the "opening date" of a NEW trade.

I don't see a field called "opening date" in the Trade Details table. I don't know where that 05/10/2023 date is coming from since it does not show up in the Trade Detail form view.

In your table view for Trade Detail table where is the data for the Trade Date column coming from? Was this column name changed from the default?

You have to match the correct fields. It looks like you want to find records in Closed-Roll Data that matches 05/10/2023, but the field called Trade Date has data of 04/03/2023. You need to figure out this difference.