[GNC] Start up cost in GnuCash

[flywire]

Common advice is don't mix personal and business bank accounts but almost
everyone does with personal tax. You could do what you want with a business
account under each top-level account or bank account then report against
those accounts but it would be fiddly.

It is a classic class issue, ie one set of books, classify transaction
splits as required, and run standard reports on the class. As Adrien
Monteleone said a couple of days ago (
https://lists.gnucash.org/pipermail/gnucash-user/2023-January/105195.html
point 2 ), you can use any free-form 'tag' in your transactions but it is
only supported by the Transaction Report with filters.

You would likely be better off using software that supports classes. iirc
https://kmymoney.org/ does.