ShaunJ beat me to it, but having looked at the register I also wondered if it might be Non-Parishioner - these entries are in the parish of Woodkirk (West Riding of Yorkshire), but are for people from other parishes. The complete register can be seen at Ancestry.
They seem to be a particular concern of Ellis Palmer, the officiating minister, and there are others earlier that year. However, there were some from other parishes in late February who don't have N.P., and on 29 Feb a man from Woodkirk who had just P.
It's possible that non-parishioners would have had to pay a higher fee, and P. might mean Pauper (so no or reduced fees), so these notes might be to help in balancing the books. However, I can't explain why some people from outside the parish weren't marked.
