Basic PAYE Tools says never alter tax code. Really?

1. I am a director and my tax code has changed. I went to put the new tax code into Basic PAYE Tools, but it says "You must never alter an employee's tax code unless you are notified to do so by HM Revenue & Customs". Is this really correct? That a company doesn't update the tax code when an employees code changes? 2. My tax code ends in "L". I Googled this and it says it means "L (Freeport — deferment)". Why would I have been given this letter?

Hi Noone,
The 'L' at the end of the tax code isn't in relation to the freeport - deferment.
The guidance you are looking at is in relating to the category letter for National Insurance.
Both of these are completely seperate. The 'L' is standard on the end of most tax codes. 
Please see guidance here:
What your tax code means
Thank you. 
 

Thank you for answering part 2. Please can you urgently advise on part 1 as I need to submit a return soon?

Hi Noone If your tax code has changed I'm assuming you have some direction from HMRC, if you have then you would change it. If in doubt you can call the Personal Tax helpline on 0300 200 3300 to check. Thank you

No I haven't had any instructions from HMRC. I only saw that my tax code had changed because I was looking for something else on their website, and the tax code shown for this tax year was different to what it had been last year.

Hi Noone,
We would need to access your record to check why your code has changed.
You can contact HMRC to review this:
Income Tax: general enquiries
Thank you.