You operate you company's PAYE scheme and choose to make a "contribution" one quarter, and you "do it on-line".
How do you stop the irate HMRC computer sending you:
The tax people send you letters telling you about sending them a Nil payslip. Only they will then call off the dogs.
But you can't do this! Why? Because you don't have that little yellow book any more as you now "do it on-line".
And you can't use your bank to send £0.00p to the PAYE account. (Although I wonder if £0.01p would do the trick?)
Going to the "normal" HMRC pages doesn't help.
Tell HM Revenue & Customs you have no PAYE/NICs payment for any tax month or quarter by going to this page.
Note the form enforces the full syntax of the account - and on the letter the reference is "abbreviated".
So your letters reads: 123P4567
Pad the string with an 'A' and '0's so it looks like 123PA00004567, and Bob's a good un.