Usually, you become common-law for tax purposes after living together "in a conjugal relationship" for 12 continuous months. If your partner is your child's parent, or has custody and control of your child and your child depends entirely on them for support, you may be common-law even sooner.

When your marital status changes ("common-law" is a marital status), you should the CRA know by the end of the following month. The easiest way to do this is by updating your CRA account. Your benefits may change because the CRA will now use your "family income" to calculate them.

People who don't update the CRA in a timely manner often finding themselves having to repay some benefits.

Going forward you will each still file your own individual tax returns. That said, you might find it easier to "link your returns" or "file together" in Better Tax so we can help your household find some tax savings.