Invoicing - percent of labor not taxable

[Matthew Pressly]

Our state tax laws are such that most of the work that I do is 
considered "data processing" of which 20% is exempt and 80% is taxable. 
Is there a good way to configure GnuCash to handle that when making an 
invoice?

I've thought of several approaches, but none seem very satisfactory:

  * Make one line item in the invoice that reflects 80% of the labor
    cost and mark that as taxable, then enter a separate line item for
    the remaining 20%, so that every invoice has 2 line items. The
    problem with this approach is that the line items no longer reflect
    what was done (a description of the work completed) but rather are
    used mainly to separate the taxable and non-taxable charges.
  * Similar to above, I could just duplicate every line item (so if
    there were 5 items, there would become 10) to make a taxable and
    non-taxable line item for each piece of work completed. But that
    seems cumbersome and would likely be confusing to clients.
  * Another approach could be to set the tax rate to 80% of the actual
    tax rate.

Do you have any other suggestions about how to approach this?

I've searched quite a bit for an answer for this question (both in 
GnuCash and with other, separate invoicing products) but haven't been 
able to find anything conclusive.

What I'm currently doing is using a spreadsheet template for invoicing. 
I've added separate columns for the 80% taxable and 20% non-taxable 
breakdown of each item, then compute tax accordingly. This works, but it 
is cumbersome.


--
Matthew