If you have concerns about the paternity of your child you should seek legal advice specific to your situation. It may be necessary to consider DNA testing either on an agreed basis or as ordered by the Family Law Courts if the other parent will not co-operate. Determining the parentage of your child could be crucial not only with respect to child support payments but the ongoing parenting relationship with that child.
The testing procedures are relatively straight forward with mouth swabs from the child and parents rather than invasive blood testing. The procedures require very strict compliance with documentation and identification, including photographic ID.