We needed to sent an EPS to reclaim recoverable amounts, but it wasn't possible to back date it to the correct month and we had to send on the current month. This caused endless issues with HMRC who allocated the full amount to that month, leaving outstanding amounts on the previous two months which had recoverable amounts due.
Hey Sandra - The EPS will not be taken into account for that period and you’ll have to pay the full amount due from your FPS. When the EPS is received it will be taken into account against the next period. - https://www.gov.uk/government/publications/basic-paye-tools-employer-payment-summary-eps-only/basic-paye-tools-employer-payment-summary-eps-only#Step2