Should I inform HMRC of errors in CT return?

I've found errors in my CT return that is out of date to amend. The reason was using estimated figures. The effect is to reduce both my Corporation Tax liability and double taxation relief claim. Should I inform HMRC of this error?

Hi
You should contact us either using the digital disclosure service available at
Ways to make a disclosure or by writing to:
Corporation Tax Services,
HM Revenue and Customs,
BX9 1AX.  
Even if the adjustment to the double taxation relief claim would offset the under-declaration of corporation tax, the company is obligated to notify us to ensure the record is correct.