Additional FPS

There was an error in our payment system for March so employees were paid on 27th March rather than 28th March.
We reported the payment date as 28th March in our FPS so we need to send an additional FPS to amend the payment date.
We understand that as long as we send the correction before 19th April this will update the March information - is this correct?
Our main concern is that the corrected FPS will include all the payments which were included in the original FPS (but with the payment date amended), we don’t want HMRC counting two payments in the period i.e. the employee being allocated two salaries for the month of March - will it just pick up the amended payment date?
Many thanks

Hi vhart
You can send an amendment at any point but we would suggest speaking to your software provider for guidance on how to do this correctly. 
Pay periods run from 06 of each month to the following 05 of the next month.
Thank you.