Double employement

Hi. My last employment appears twice on HMRC. After termination, the company realised they still owed me money so they gave me another months pay. However now I have 2 employments with the same company though, in reality, it was 1 employment and an extra pay due to a mess up on their side. Should I merge these two employments or keep them as is?

Hi kloeriou sacm,
Keep them a two employments to match the information submitted by the employer. 
Thank you.