The mechanics run through your financing condition. CMHC and the other insured lenders behind a Saskatchewan mortgage lend against the lower of purchase price or appraised value, so if you offered $450,000 and the appraisal comes back at $430,000, the mortgage is calculated on $430,000 and the $20,000 difference has to come from your own funds if the deal is going to close as agreed.
Covering it makes sense when the comparables genuinely lag a fast moving market, when the property has documented improvements the appraiser did not credit, or when losing the house means starting the search over in a market where the Saskatchewan REALTORS Association is reporting 1.63 months of supply. It makes far less sense when the gap reflects a bidding war that outran the actual evidence of value.
Before deciding to cover anything, ask whether the appraisal can be challenged with better comparables or documentation of work the appraiser missed, because that route can close the gap without you spending a dollar. Joel Dyck prices listings against sold comparables up front specifically so buyers and sellers see fewer surprises at this stage. Get your hand-reviewed valuation from Joel Dyck.