Form BSF186A (or B4A): This is a goods-to-follow list and is used to track all the items that will be arriving in Canada separately –
either on the day of your arrival
or after your arrival
. You should fill this form if you’re having any of your belongings shipped. If you don’t complete this form and your goods arrive at a later date, you may have to pay duty for importing them into Canada. One of the major benefits of completing form B4A and getting it stamped by the CBSA offer is that your goods will qualify for duty- and tax-free importation into Canada.
https://arrivein.com/daily-life-in-canada/how-to-fill-forms-b4-and-b4a-bsf186-and-bsf186a-while-moving-to-canada/#:~:text=Form%20BSF186A%20(or%20B4A)%3A,arrival%20or%20after%20your%20arrival.