No.  Your tenancy will not be invalidated or made ‘null and void’ by any notice served by your landlord.

The notice may be invalid though – but it depends on the type of notice that was served:

If the notice was a section 21 notice

Then the notice will probably be invalid if the notice period ends before the fixed term. 

So if your landlord were to issue proceedings for possession based on it – you would probably have a defence. 

Although if this was clearly a typo type error the court might allow it – provided the court proceedings were not started until after the fixed term ended.

If the notice was a section 8 notice

Then for some grounds (in particular the serious rent arrears ground) the notice can expire before the end of the fixed term.  Which will allow your landlord (if the arrears are not paid) to bring proceedings to evict you before your fixed term has ended – provided your tenancy agreement provides for this.

We have some guidance on the different notices in the article with help for tenants facing eviction below.

You may want to seek legal advice – you can either use our telephone advice service or find someone on our further services page (both linked below).