How pensions, and retirement funds are taxed from Canada depend on source (government or private). Where are your clients funds from?. If from Government (like our SS) you report it same as our SS (some may be taxable or not depending on other income. If from a pension from a private company it will be double taxed, and you report it on 1040 schedule 1. Use 1116 to get a credit on that double taxed income. If from investment (like our IRA's) Do same as pension. The above is my interpretation of the treaty, but you need to research yourself.