Tax question - Medical expenses - Orthodontic treatment

You can claim the amount you paid in 2015 minus the amount your plan reimbursed you. If you had to pay the whole $5000 up front, you would claim 5000-1200= 3800. If you paid half in 2016, you would claim $2500-600= 1900, and the balance on 2016 tax return. Keep all receipts.

http://www.cra-arc.gc.ca/tx/ndvdls/tpcs ... ml#rthdntc

I wonder who determines whether it is purely cosmetic??

By the time most people deduct the $2208 and apply the 15% to calculate the benefit, the value is so small that I doubt the CRA bothers to audit whether or not the orthodontics are "cosmetic."

I claimed braces for my daughter & my wife before (minus insurance covered amounts) on 2 occasions and never got questioned by CRA. You can't really say it's cosmetic because in my wife's case, the dentist recommended or else, she may lose couple of teeth in a few years due to prolong overbite causing the problem. If you can effort it, try to pay it all in one year to maximize your credits

Claim what paid in a given year less any reimbursement from dental plan.

Medical is for any 12 month period and not just calendar year. If you want to maximize the Ortho claim ensure to pay the entire $5k within those 12 months.
Example
Pay $1500 in Sept 2015, Pay $500 Oct 2015, Pay $500 Dec 2015, pay $500 Jan 2016, pay $500 Mar 2016, pay $1500 Aug 2016

2015 return- Claim nothing and use Sep 2014 to Aug 2015 as date for medical in your return
(if you claim Jan to Dec 2015 for $2500 you will probably net you nothing or very little, anything over 3% of income)
2016 return - Claim Sept 2015 to Aug 2016 which would be $5,000 less any reimbursement. Load up on all medical payment before end of August 2016

Just remember, Medical is just a tax credit and not a deduction from income