Hi,
I'm a teacher, and not a lawyer. You might wish to post your query again in our Legal English area of the Forum.
1.On the day of September 15, 2007 in *** the Sales Agreement has been concluded between:.. IS IT OK TO WRITE "HAS BEEN"? No.
On September 15, 2007, in *** , the Sales Agreement was concluded between:..
2. The subject of the Agreement shall be issued to the Buyer in the original producer’s packaging. Seems OK
3. The payment day shall be the day of debiting the Buyer’s account. Seems OK
In everyday, non legal-style English, don't use all these capitals.
Best wishes, Clive