[Dolibarr-dev] witholding tax (from forum)

[Elettrico]

Hi,
I'm an italian developer at Diciannove Società Cooperativa.
We are using dolibarr for years and we are thinking to put the
modifications we need in a module and the release it under open source
license.
One of the mos important is the "ritenuta d'accordo", it works like the
witholding tax (there's a thread in the forum talinkg about that), for
example I can have a receipt (facture) like that:

- first row                     100
-       vat                      20
- second row                    200
-       vat                      40
-       witholding tax           48
- third row                     300
-       vat                      60
-----------------------------------
- total                         600
- vat                           120
- witholding tax                 48
-----------------------------------
- total to pay                  720
- withold to pay                 48

it means that I can have rows with a witholding tax or not and then I
have to consider this tax not to be paid with the receipt (I'll pay only
total+vat), but I have to consider it because I'll have to pay it like a
tax.

Another important thing is that we have "iva differita", it means that I
can emit a receipt with a VAT that I can pay only when the receipt is
paid to me.

So, due to the forum posts, witholding tax is being implemented in the
future version of dolibarr, where can I see this implementation or where
I can we have more information? Like the release date, or something
about how it will work?

Talking about that: which is the best way to "expand" an object in
dolibarr? Do I have to duplicate the receipt module if I "only" want to
add a field and a checkbox on the form?

Thank you for your good work.
Fabio Moretti