I'd probably just use that statement but add it to every delivery address line just updating the address line number

If I understand you correctly you mean that you get a mix of address details because only some of the delivery address fields are blank? For example delivery address line 1 is populated so you get that line as expected, but then delivery address lie 2 is blank (legitimately as the address has no line 2) but because of your if statement you actually get invoice address line 2.

If that is the case there are 2 possible approaches. The simplest one would be if you can guarantee that delivery address line 1 would never be empty if populated i.e. you'd never have a blank line 1 but a non-blank line 2. If this is the case then you simply need to check address line 1 for each line. So your formula for address line 1 would be exactly as you have already:

SALES_ORDER.DEL_ADDRESS_1= "" ? SALES_ORDER.ADDRESS_1:SALES_ORDER.DEL_ADDRESS_1

And the formula for address line 2 would be:

SALES_ORDER.DEL_ADDRESS_1= "" ? SALES_ORDER.ADDRESS_2:SALES_ORDER.DEL_ADDRESS_2

NOTE that the field we check for empty does not change in that formula and remains a check on line 1. It is only the result that changes to address line 2.

Then simply lather-rinse-repeat for the remaining address lines.

If however you do have a situation where delivery address line 1 might be blank but address line 2 (or any other line) is not, then you'd need to resort to a more complex formula. This would make address line 1 something like this:

SALES_ORDER.DEL_ADDRESS_1 = "" And SALES_ORDER.DEL_ADDRESS_2 = "" And SALES_ORDER.DEL_ADDRESS_3 = "" And SALES_ORDER.DEL_ADDRESS_4 = "" And SALES_ORDER.DEL_ADDRESS_5 = "" ? SALES_ORDER.ADDRESS_1:SALES_ORDER.DEL_ADDRESS_1

And address line 2 becomes:

SALES_ORDER.DEL_ADDRESS_1 = "" And SALES_ORDER.DEL_ADDRESS_2 = "" And SALES_ORDER.DEL_ADDRESS_3 = "" And SALES_ORDER.DEL_ADDRESS_4 = "" And SALES_ORDER.DEL_ADDRESS_5 = "" ? SALES_ORDER.ADDRESS_2:SALES_ORDER.DEL_ADDRESS_2

Again the only thing that changes in the formula is the result which becomes line 2. The conditional check remains the same.

Apply the same logic to the remaining address lines and you should be good to go with no mixing of delivery/invoice address data.

Hope that helps

Thank you very much  I'm very new to report designer so this has been a massive help.