Did you buy the mare and just didn't register her or did you breed a mare to someone else's stallion and didn't register the foal? Or did you buy a mare in foal.
If you bought the mare and didn't register her then you will need an application signed by the previous owner, a transfer signed by them and a request for DNA kit. The mare has to be PQ before she can be registered no matter how you got her. That would be Registraiton - $60, transfer (late) $25 and DNA $41 = $126
If you bred a mare to someone elses stallion you will need an application signed by you, a breeders certificate signed by you as the mare owner and signed by the stallion owner and a DNA kit. Registration - $60 DNA - $41 = $101. You do need the breeders certificate though.
If you bought a mare in foal then again, Registration $60 DNA $41 While you would sign the application as the owner of the mare at the time of foaling, the breeders certificate would have to be signed by the owner of the mare at the time of service and the owner of the stallion at the time of service.
This is why its just so much easier to register foals before they are 4 months old for the low price of $20.