You ALWAYS use capital letters for provinces and territories abbreviations.
Provinces
BC = British Columbia QC = Quebec
AB = Alberta NL = Newfoundland and Labrador
SK = Saskatchewan NB = New Brunswick
MB = Manitoba NS = Nova Scotia
ON = Ontario PE = Prince Edward Island
Territories
YT = Yukon
NT = Northwest Territories
NU = Nunavut
Provinces
BC = British Columbia QC = Quebec
AB = Alberta NL = Newfoundland and Labrador
SK = Saskatchewan NB = New Brunswick
MB = Manitoba NS = Nova Scotia
ON = Ontario PE = Prince Edward Island
Territories
YT = Yukon
NT = Northwest Territories
NU = Nunavut