US-Canada Totalization Agreement: how do I combine work credits for Social Security and CPP?

The Agreement on Social Security between Canada and the United States does two things. First, it prevents you from paying into both countries’ social security systems on the same earnings by assigning coverage to one country. Second, it lets you combine work credits earned in both countries to meet the minimum eligibility thresholds for benefits: 40 quarters for US Social Security, roughly 10 years of contributions for CPP. The agreement has been in effect since August 1, 1984, and it covers Social Security (OASDI) on the US side and the Old Age Security program plus CPP on the Canadian side. Quebec sits under a separate US-Quebec Understanding that covers QPP.

Which country’s system am I in?

For employees, the default is the country where you physically work (Article V(1)), regardless of where the employer is based. For self-employment, coverage follows your country of residence (Article V(6)).

• Temporary assignments: Article V(2)(a) keeps a worker sent abroad for up to 60 months under the sending country’s system; a Certificate of Coverage proves the exemption
• Past five years: coverage switches to the work country, though Article V(11) allows extensions by mutual agreement
• Self-employed example: a US citizen living in Toronto and billing US clients pays CPP, not FICA; the full analysis is in do I pay both US self-employment tax and CPP

Situation	Covered under	Authority
Employee working in the US	US Social Security	Article V(1)
Employee working in Canada	CPP (or QPP in Quebec)	Article V(1)
Employee temporarily sent to US, assignment under 5 years	Sending country (Canada)	Article V(2)(a)
Employee temporarily sent to Canada, assignment under 5 years	Sending country (US)	Article V(2)(a)
Self-employed, resident in the US	US Social Security	Article V(6)
Self-employed, resident in Canada	CPP (or QPP)	Article V(6)

How do I get a Certificate of Coverage?

The certificate is what proves the exemption to the other country. Without it, the employer or the self-employed worker has no documented basis for not paying into the other system. The SSA states that employers and self-employed workers “must request a certificate of coverage to establish an exemption.”

Which authority issues it depends on which country’s system you’re staying in:

• Staying in US Social Security (US employer sends you to Canada): request from the SSA’s Office of International Programs. The SSA issues Form USA/CDN 1, which you present to the Canadian employer or CRA.
• Staying in CPP (Canadian employer sends you to the US, or self-employed living in Canada): request from the CRA on Form CPT56. The CRA issues the certificate, which you attach to your US return.
• Staying in QPP (Quebec resident): request from Retraite Quebec on Form QUE/USA 101.

Request early. The SSA advises requesting the certificate “preferably before work in the other country begins.” The effective date generally runs from when the work started, not from when you applied, but the proof arrives faster when you don’t wait.

For self-employed workers, the SSA specifies that you “should attach a copy of the certificate of coverage to [your] U.S. tax return every year as proof of the exemption.” This is an annual requirement, not a one-time attachment.

What’s “totalization” and how does combining credits work?

Totalization lets you combine your periods of coverage in both countries to meet either country’s minimum eligibility threshold. If you worked in both countries but lack enough credits in either one alone, the agreement counts your foreign coverage toward the domestic requirement. The combining is only for eligibility; each country calculates its own benefit based on its own credits.

• US Social Security requires 40 quarters (~10 years). You need at least 6 US quarters before the SSA will totalize; CPP years count toward the remaining quarters
• CPP requires at least one year of valid contributions. Most people who worked in Canada meet this, but totalization can bridge the gap if you left young

How is the benefit calculated under totalization?

Each country computes a “totalized” benefit using a pro-rata method:

1. Theoretical benefit. The country calculates what your benefit would be if all your combined credits had been earned under its system.
2. Pro-rata reduction. It then reduces that theoretical benefit in proportion to the credits you actually earned under its own system, compared to the total.

The US version: the SSA computes what your Primary Insurance Amount (PIA) would be if all your combined US and Canadian credits were US credits, then multiplies by (actual US quarters / total combined quarters). You receive that fraction as your US Social Security benefit.

The Canadian version: Service Canada computes what your CPP retirement pension would be with all combined credits as Canadian contributions, then reduces it proportionally.

What happened to the Windfall Elimination Provision?

The WEP and the Government Pension Offset (GPO) were repealed by the Social Security Fairness Act (P.L. 118-273), signed January 5, 2025, effective retroactively for benefits payable after December 2023. CPP benefits no longer reduce US Social Security benefits.

• Before the repeal, the WEP reduced Social Security for anyone also receiving CPP, and the GPO reduced spousal/survivor benefits by two-thirds of a government pension
• If you were receiving a reduced benefit, the SSA should have recalculated; contact the SSA if you haven’t seen the adjustment

Does the agreement affect my income taxes?

No. The agreement is a social security agreement, not a tax treaty. It determines which country’s social security system covers your earnings (and therefore which contributions you pay). Income tax is governed by the US-Canada tax treaty and each country’s domestic law. The two interact at one point: the FICA exemption affects your W-2 and the CPP contributions affect your T4, but the agreement changes nothing about how your income is taxed.

• For the tax treatment of CPP and OAS benefits once you are receiving them, see how CPP and OAS are taxed if you live in the US
• Under Article XVIII(5) of the tax treaty (restored by the 1997 Protocol), Social Security and CPP/OAS benefits are taxable only in the recipient’s country of residence: US Social Security paid to a Canadian resident is taxable only in Canada (with 15% of the benefit exempt from Canadian tax), and CPP/OAS paid to a US resident is taxable only in the US

What about the FICA exemption for employees?

When the agreement assigns coverage to one country, the other country’s contributions do not apply. For employees, IRC 3101(c) and IRC 3111(c) exempt wages that are subject to the other country’s system under Section 233 of the Social Security Act. The mirror provision on the Canadian side exempts the employee from CPP on US-covered earnings. The certificate of coverage is what the employer uses to justify not withholding; without it, there is no documentation to support the exemption.

• IRC 3101(c) covers the employee’s share; IRC 3111(c) covers the employer’s share

Can I apply for benefits in both countries?

Yes. You can receive benefits from both US Social Security and CPP simultaneously. Each country pays based on its own credits (pro-rated if totalization was needed to qualify). With the WEP repeal, there is no reduction to your US benefit for receiving CPP.

Apply in each country separately. For US Social Security, apply through the SSA (online at ssa.gov, by phone, or in person). For CPP, apply through Service Canada. If you need totalization to qualify, mention that you have credits in the other country when you apply, and the two agencies coordinate the verification.

What should I do next?

If you are working across the border, verify which system covers your earnings and get the Certificate of Coverage before filing season. If you have worked in both countries and are approaching retirement, check your credits in each system (US: my Social Security, Canada: My Service Canada Account) and determine whether totalization is needed.

• For the self-employment overlap question (FICA vs CPP), see do I pay both US self-employment tax and CPP

• For the tax treatment of benefits you are already receiving, see how CPP and OAS are taxed if you live in the US

• How are CPP and OAS taxed if I live in the US?, the tax treatment that applies once you’re actually receiving the benefits

• When should I claim CPP vs Social Security?, the claiming-age strategy once you know your credits in each system

• Cross-border tax in Montreal, where QPP (not CPP) applies and the totalization agreement routes through Retraite Quebec

• Self-employment tax: CPP vs FICA, how the totalization agreement exempts SE tax for US citizens working in Canada

• Cross-border payroll and employer obligations, the employer side of the certificate of coverage and dual withholding

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.