Why does the transaction detail report smaller numbers than the invoice?

Hi there, @travelbug.

Thanks for reaching us out here in the Community. 

The Transaction Detail report is the breakdown of a specific transaction with your accounts. You can check on the Invoice itself and click CTRL+Y on keyboard. This will give you the Transaction Journal of the invoice, which is exactly what's on the Transaction Detail Reports.

This should information provide you the details of your transactions. 

You've got me here if you have any additional question about this concern. I'll be around to provide further assistance. Have a great day!

@BettyJaneB

Please Learn from the input here.

You see allocated amounts when you run Detail reports on Cash basis. You also see Allocated amounts if you put a Negative in the Invoice or applied either a Credit Memo or a Prior Payment or Partial Payments. That's because Cash Basis reporting is for the Date of the Payment and the allocation when it isn't simply One Amount paid in full, is going to work like this:

$100 Widget sales + 7% taxes = $107 total owed.

I get paid $50. Now everything on the invoice is $50/$107 paid, or about 47%. Even the Sales Taxes are 47% paid.

If you don't want that detail, then top left, run Accrual basis reports. If you need "only if paid" then Filter on Paid Status, not Cash Basis.

Please see my attachment.