Président Mitterand est mort

[Crack1]

Si je ne me trompe, Président Mitterand est mort en 1996.
If I am not mistaken, President Mitterand died in 1996.

I know the subordinate sentence is fine. How about the main clause?
Please correct me.

[Frank]

The main clause is ok, but sounds a bit snoby, you should add the "pas" to make it sound more natural:

Si je ne me trompe pas, ...

Some variants include :

Sauf erreur de ma part, ...
Si je ne m'abuse, ...

Two excellent expressions to know, they are very useful and they can be used in any context.

[Neil Coffey]

Frank -- I'm just intrigued... so are you saying that si je ne me trompe sounds more snobby to you than si je ne m'abuse?

[Frank]

Hi Neil,

If you could (and, in everyday speech, would) add the "pas", but you don't, it definitely sounds very snoby.
Here, we would say "je ne me trompe pas". Skipping the "ne" is not biggie ("j'me trompe pas"), but skipping the "pas" was okay in French from centuries ago, but would be really snoby nowadays.

On the other hand, for some reason, "si je ne m'abuse" is almost always used as-is, without the "pas". So using the negative form with "ne" but no "pas" sounds normal here, not snoby at all.
And "si je ne m'abuse" is rather common, in any context. "Si j'm'abuse c'est toi qui a bu toutes les bières qui étaient dans le frigo ?"