Since you are asking on HN, I'm assuming you are not looking for legal advice, just other's opinions. Obviously, you should talk to a lawyer, but here's my free

Since you are asking on HN, I'm assuming you are not looking for legal advice, just other's opinions. Obviously, you should talk to a lawyer, but here's my free internet advice (I'm not a lawyer). My advice also makes assumptions that Canadian law is very similar to US law, which may not be true. You have three options: do nothing, settle, fight. It sounds like you only got an infringement letter. These are normally sent out in bulk by patent trolls to any and all people they think they can extort money from. There is no legal burden to this letter. You don't have to talk to them (and you shouldn't). Don't respond to the letter. Don't take their phone calls. Refuse to talk to them. Regardless of whether you hire a lawyer or not, at this point, there is nothing to be gained by approaching them. Eventually, they will call you. They have armies of hourly workers who go through the database of people they sent out the letters to and try to get an easy settlement from you. Don't sweat these calls. They'll ratchet up the threats via voicemail (since you are not talking to them). And eventually they'll have to make a decision. Patent trolls are in the business of making money. Lawsuits are expensive. If the cost of a lawsuit is greater than the amount of money they think they can get out of you, they won't sue you. It would be bad business. From your description, I'm guessing it would be a bad idea for them to sue you because you don't really have a lot to offer them. Even if your app makes a couple hundred thousand dollars, they won't bring a suit against you. It's a waste of their time. (They'd happily take a settlement check from you though). If you thought there was a good chance they were going to sue you (which I don't), and you were located in the US (which you are not), and it looked like they were going to bring suit in that horrible district in Eastern Texas, you could decide to file suit against them first in another venue to avoid having your suit take place there. It doesn't look like Canada has this same issue (patent troll friendly district where most cases go for the patent trolls). In essence, at this point, if you go to a lawyer and have them draw up a defense that says your tech doesn't infringe, you'll end up spending between $5,000 and $10,000. I don't think it's really worth it right now. My advice would be to wait until you get some sort of actual legal notification of a suit. Before that point, it's all just posturing and bluffing. Plus, you can still settle at that point (you might have to pay a bit more though to cover the added costs they've spent).