Basically, if you aren’t claiming any credits, and don’t have to pay any taxes, you don’t need to file a return. The CRA has a full list here of when it is required to submit a return in Canada: https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/you-ha...
If you are still not sure if you need to submit a return, or you do need to send in a return and need a SIN, you can call the Canada Revenue Agency (CRA) at 1-800-959-8281.
If you don’t need to submit a return, then your husband would prepare just his own return (separate), though he can still choose “Common Law” and include info about you as his spouse.
