1) What is Irregular Pay?
The Irregular Pay is not a pay frequency. It is just an indicator indicating that the employee concerned is not being paid regularly in an FPS returns.
The Irregular Pay refers to employees' who aren't paid on a regular basis and are unlikely to be reported on regular FPS for three months or more. As per HMRC you need to set an Irregular Payment Indicator to indicate the employee is paid on an irregular basis and has not left the company. Further If you don't set the irregular payment Indicator for employees not paid at least once every three months, or is not reported on each regular Full Payment Submission (FPS) then HMRC will assume that the employee has left.

Note: If an employee is paid infrequently, but regularly, say every three, six or 12 months, then there is no need to set the irregular payment indicator.

For more Information please Click on the HMRC Links
http://www.hmrc.gov.uk/payerti/reporting/what-to-report/irregular-payment.pdf,
https://www.gov.uk/what-to-do-when-an-employee-dies/paying-employee-died

2) Who is qualified for Irregular pay?
The Irregular pay is basically made to,

• Casual or seasonal employees'
• Employees' on long term sick leave
• Employees' on maternity leave
• For any employee who for any reason will not be reported on an FPS for a period of three months or more.
  

3) How to make Irregular Pay in the application
If you have an employee paid on the irregular basis then you need to set the Irregular Payment Indicator while creating the Employee or Editing the Existing Employee Employment Details in the application, Process the payrun selecting the appropriate pay frequency and E-File the FPS as shown in the Road Map below.

Note: The Irregular Payment is not a pay frequency rather it is only an indicator to indicate Irregular Paid employees' irrespective of any pay frequency they are paid.

Road Map – New Employee - To make an Irregular pay E-Return (E-File) to HMRC for a New Employee
Step 1: Go to the Employee Menu in the tasking Zone and click on the Add New Employee.
Step 2: Enter the employee details and tick the Irregular Payment Indicator check box.
Step 3: Click on the continue button, enter the details and later click on the finish button.
Step 4: Further you need to process the payrun selecting the appropriate pay frequency as shown in the "Road Map - ''Processing Employees Pay" and E-File the regular FPS as shown in the "Road Map for E-filing FPS to HMRC".

Employee -> Add New Employee -> Employee Employment Details -> Tick the Irregular Payment Indicator check box -> Continue button -> Continue button -> Continue button -> Finish button
( ' Employee ' is the button positioned in the tasking zone menu at the top. It is the second button from the left)

Road Map - Existing Employee - To make an Irregular pay E-Return (E-File) to HMRC for an Existing Employee
Step 1: Go to the Employee Menu in the tasking Zone and Select the Submenu View / Edit Employee Details.
Step 2: Click on the View/Edit link horizontal to the Employee for whom Irregular Payment Indicator has to be set.
Step 3: Click on the Employee Employment Details - View/Edit button and later click on the Edit button.
Step 4: Now tick the Irregular Payment Indicator check box and click on the save button.
Step 5: Further you need to process the payrun selecting the appropriate pay frequency as shown in the "Road Map - ''Processing Employees Pay" and E-File the regular FPS as shown in the "Road Map for E-filing FPS to HMRC".

Employee -> View / Edit Employee Details -> Action -> View/Edit -> Employee Employment Details -> Edit -> Irregular Payment Indicator -> Tick the Irregular Payment Indicator check box -> Save
( ' Employee ' is the button positioned in the tasking zone menu at the top. It is the second button from the left)

Road Map - Processing Employees Pay
Step 1: Go to Payrun menu in the tasking Zone and Click on the submenu Process Pay.
Step 2: Click on the appropriate Pay Frequency, choose the employees' and Enter the pay details.
Step 3: Now Click on the "Save Data & Process Pay" button and Continue button.
Step 4: Click on the Approve Pay Data button and Update YTD button.

Payrun -> Weekly / Monthly / 2 Weekly / 4 Weekly / Quarterly / Annual / Bi-annual -> Save & Process TimeSheet Data button -> Continue button -> Approve Pay Data button -> Update YTD button
( ' Payrun ' is the button positioned in the tasking zone menu at the top. It is the fourth button from the left)

4) How to report Irregular pay to HMRC (FPS E-Filing)?
You can follow the Road Map mentioned below to make an Irregular pay E-Return (E-File) to HMRC,

Note: If you make the payment after the employee leaves, then the NICs treatment for irregular payment (such as an unexpected bonus or accrued holiday pay) has to be done using the usual rates, limits and National Insurance category letter but with a weekly earnings period.

Road Map – E-filing FPS to HMRC
Step 1: Go to the E-Filing EOY/RTI Menu in the tasking Zone and Select the Submenu "E-file RTI EAS, FPS, EPS, NVR".
Step 2: Click on the FPS (Full Payment Submission) link.
Step 3: Select Pay Frequency and Pay Period and Proceed with the process.
Step 4: Further you can click on the "Live E-Filing" button and E-File the FPS.

E-Filing EOY/RTI -> E-file RTI EAS, FPS, EPS, NVR -> FPS (Full Payment Submission) link -> Continue button -> Confirm button -> Live E-Filing button
( ' E-Filing EOY/RTI ' is the button positioned in the tasking zone menu at the top. It is the third button from the left)