Ontario regulated plans
Before January 1, 2012, there was no standard form that you could use to get the pension valued. So you had to hire someone like an actuary to value the pension.
After January 1, 2012, you use a standard form to ask the plan administrator of an Ontario regulated pension plan to value a pension, unless you have a court order, arbitration award, or domestic contract that was made before January 1, 2012.
Because you're not married, you and your common-law partner are don't automatically share a pension.
But, if you're going to share a pension, only the pension plan member can ask for the pension to be valued by filling out a Form 1 - Application for Family Law Value. They may also need to fill out other forms.
If you need help filling out the form, the Financial Services Commission of Ontario has a Family Law Forms page that has a User Guide for each form and Q&As for some of them. Form 1 also has a video tutorial.
Part E of Form 1 asks for a "Starting Date of Spousal Relationship (Married or Common-Law)" of your spousal relationship. This is the date that you and your common-law partner started living together unless you have a court order, arbitration award, or agreement with a different date. Then a later date can be used.
Part F of Form 1 asks for a "Separation Date (Family Law Valuation Date)". This is usually the date of separation. You can provide one date or, if you and your common-law partner don't agree on the date, you can provide 2 potential dates. If you provide 2 dates, then you and your partner both need to fill out some of Form 1. Your application is then treated like 2 applications, with each application using a different date.
The plan administrator can charge a fee for valuing the pension. Depending on the type of plan, they can charge from up to $200 to $800. If you and your partner have asked for 2 valuations based on 2 different dates of separation, you may both be charged a fee.
After the plan administrator receives the completed application and the fee, if any, they have 60 days to provide a "Statement of Family Law Value" form. This form is sent to both partners and gives the value of the pension. If you and your partner have asked for 2 valuation based on 2 different dates of separation, you get 2 "Statement of Family Law Value" forms.
Federal public service plans or federally regulated plans
Each pension plan is unique. You may be able to ask the pension administrator to provide you with an estimate. You can also hire a financial professional, usually called an "actuary", to value the pension.