Do you travel back and fourth between Canada and your current place of residence abroad? Why are you living abroad? Are you studying? Working? Wanted to be closer to your partner? All of these come into play. It becomes an issue particularily if you live abroad and are earning income but not declaring it in your taxes. It becomes an issue of tax evasion. If you have been declaring your income and assets abroad in your taxes then it becomes much less of an issue. If you do not earn income or have assets outside of Canada then it becomes easier to sort this thing out.
I declared my spousal status after I filed for my 2012-2013 taxes, which makes sense because I was married in June 2013. CRA accepted my declaration of change in marital status and told me that it doesn't matter in terms of my GST or whatever, I wasn't married when I filled in 2012-2013 and my GST etc will be adjusted the following year to reflect my marital change when I declare it on my tax return. So, no need to worry that it took me six months to declare this change so long as it was reflected in my 2013-2014 taxes.
But CRA did advise me to declare my change in status to child benefits, which would be adjusted immediately. When I did that they had to reassess my benefits. In fact, verbal wasn't enough. I had to send them a letter declaring my change and how much my husband earns abroad, which I took my sweet time to do, and then they sent me a letter telling me I owed them like $2000+ unless I declared my husbands income. Anyways, I did send them a letter with the income and within a few months I received payments again adjusted for my husband's added income. So consider whether you receive any other benefits. An accountant would be the best person to chat to before contacting CRA. Also, I am aware of a couple (family friends) whose inland application was held until they sorted out some tax repayment issues. So, that suggests to me that CRA and CIC may work closely together and CIC may look at your tax return for more than just whether or not you've accepted welfare/social assistance, but looking for clues that you didn't pay certain taxes. ....just my thoughts and experiences. I am no expert. Good luck.