question about transaction and taxes

[danilo lujambio]

Hi,

here in Argentina we have a tax named IVA (21 %) which when it is paid  you
have a fiscal credit  equal to  21 percent  of  the amount the transaction.

For example if you bought something at $ 121 , the real cost is $ 100 and
you have  $ 21 of a fiscal credit.

Now we are using gnucash to follow this , making two transactions

we bought something at $ 121 , we put in the account (equipment to sell) $
100 from our cash box and put in fiscal credit acount $ 21 from our cash box

we are needing to concentrate this in one transaction . Is there any way to
put $ 121 in some account and automatically gnucash put $ 100 as a real
value and $ 21 in our credit fiscal account , and take $ 121 from our cash
box ?

thanks ! and sorry by my english :-)