In order to be considered as being in a common-law relationship you have to live together for at least 12 months in a conjugal relationship. Alternatively, if you live with someone who is the parent of your child by birth or adoption you are automatically considered to be in a common-law partnership with them. It’s important to remember that you may be required to prove that you’ve been living in a common-law relationship, whereas while legally married the marriage certificate acts as the proof.