Hi Abraham. Unlike humans which are pretty good at catching spelling errors, Access needs exact spelling and syntax. You need to double-check your spelling. You spelled "statement" wrong in the subject for this post (which I left so you'd see it) and you spelled "IsTaxable" wrong in your code. This is important. Also, the IIF function doesn't use semicolons at all. It should be:

IIF(IsTaxable, A, B)

So double-check all of your spelling. Don't be embarrassed. Spelling is the NUMBER ONE reason why people have code that doesn't work.

I have in first place worked as you trained me by using normal commas, but unfortunately, it did not work, then when I downloaded from your web the database I looked in it and found that by the IIF function are actually semicolons instead of commas...
I use Microsoft 365 so maybe that differs...

just googled now
In Europe, the Comma is used as a decimal separator, and therefore a Semicolon is used as a column separator
I think you should put on my name my country's flag...

Yep. You're right. I didn't realize you were in Austria. That's another reason why I like the flags on peoples' accounts. I only did the top 15 or so (where my students are from). I'll get Austria added as soon as I can.

You're right. In a lot of Europe, the comma is the decimal separator, and the semicolon is the list separator. You can actually change these settings in Windows under Regional Settings in your Control Panel. I have a lot of European students who change just to stay compatible with US standards. In any case, let me see the complete SQL statement you have. Error 3079 usually comes up when you have an ambiguous field name in a query involving two or more tables.

Abraham, your flag is now flying. Enjoy!