Only once HMRC have agreed that they will treat your company as Dormant will you be relieved from the requirement to file a tax return.

If you have had a letter (and it is still current) and you used Inform Direct to file Dormant Company Accounts you will not need to make any other filing to HMRC.

If HMRC has not agreed to treat your company as Dormant, they may demand a tax return be filed and even fine a company for late delivery even if no tax is payable.