If you post something wrong, you must correct the entry with a reverse entry. NAV do not allow you to change posted entry. Of course, if you are familiar with Navision tables and have the Solution Developer or Vendor license, then you can change the value from the table.
For example, sometimes, users will call me to make a simple request like this:
"Hi Navision-Girl, I have posted a sales order with the wrong item description. My customer cannot accept the item description from the Item Card. Usually, I will modify the Item description before post Invoice but this time, I have forgoten and posted the Invoice before I change the Item Description. Can you please help me ?"
Without the solution developer license, I can't even change the Description field in the Sales Invoice Line table. If I tried to change the description field in the Sales Invoice Line table, Navision will throw the following error message:
"Sales Invoice Line cannot be modified in this form."
Then, I have no choice but tell the users:
"Posted Invoice cannot be changed. You may need to do a Credit Memo to knock off the Invoice and Post a new Invoice with the correct description."
If this is the first time the they make this kind of mistake, they will do the Credit Memo but with a little bit of grumbling. If the users make mistakes again for a few more times and required to do the Credit Memo everytime, they will get frustrated and make a lot of complain and scarcastic comment about Navision.
With the solution developer license on hand. I will just ask the users to submit a change request as a procedure and I will do them a favour by changing the data in the Description field. Changing description fields in posted tables is one of the simplest scenario that requires Solution Developer license.