Dates of invoice, transaction and sales tax

[Hendrik van Antwerpen]

Hello,

I'm breaking my head over all the dates involved in invoicing and sales 
tax payment. I'll describe the desired situation first, for the example 
of buying Product for EUR119 (EUR100 expense and EUR19 sales tax).

Amounts:
- Expense EUR100
- Sales tax EUR19 (can be reclaimed)

The dates involved:
- The buy happened on the 20th of August 2010 (transaction date).
- The invoice was send (late) on the 2nd of October 2010 (invoice date).
- Our book year '10-'11 starts on the 1st of September 2010.
- The sales tax period are in quarters, Q4 starts the 1st of October 2010.

Sales taxes have to be reported in the period of the invoice date, in 
this case Q4.

What I got:
- When I create an bill, I set the open date to the invoice date.
- The entry in the bill I give the transaction date.
- When I post the bill, all transactions get the invoice date. I could 
not find a  difference between accumulating splits or not.
- I found no way to report the tax entries in invoice date.

Desired result:
- The entry in my expense account should belong to the book year 
'09-'10, so it should have the transaction date.
- The sales tax entry should be on the transaction date but should be 
reported in a Q4 report because of the invoice date.

If someone knows a solution for this, I would be happy. If a patch to 
gnucash could help on this, I could do some hacking too.

Regards,
Hendrik