It can happen sometimes that when you are an employer, you have not actually made any wage or salary payments for a PAYE month such as the month from 6 February to 5 March 2019. In that case you must submit electronically an Employer Payment Summary as a NIL return by Tuesday 19 March. This bureaucratic requirement is too easy to overlook.
If you engage a local accountant and business advisor or a payroll bureau to do your wages, then this will be taken care of. In our case we keep a diary and do a batch of payrolls at about the same time each month. Our payroll files are bright yellow like the old P30BC booklet so we do not overlook them. We colour-code all the taxes so green is VAT, red is income tax, blue is corporation tax and yellow is PAYE.
If you no longer want to have a payroll scheme, then you need to close it down in a formal way. You cannot just assume that you can stop sending in monthly returns.