That's a critical piece of information you omitted. It sounds like your client is not aware of the fact that you're a Canadian citizen (?) and did not perform work in the United States.

Sometimes companies will require that you certify that you're a foreigner using a Form W-8BEN. If you're not able to resolve this issue with your client by explaining your status and it's creating issues for you, you should consult with an attorney.

It also sounds like it would be worthwhile for you to consult with an accountant who can educate you about your obligations to your clients and your subcontractors generally.

Thanks for the feedback. They're well aware that I'm located in Canada as all of that information was outlined on the initial agreement. I'm just a bit taken back as I've worked with other clients who have never asked for this. It's likely that these particular clients would like to declare these expenses/right them off to lower their taxable income, I just wish they would have mentioned this before hand so I could have prepared for this.. The sub-contractors are based in Europe so it's really a massive loss for me if I were to go that route.

Also, I've already been paid in full. So at this point I have nothing to lose really.

You still sound very confused about your obligations and your client's obligations. It sounds like you expect to keep all your transactions under the radar and not declare any of them to any tax authority. Don't.

Just for this project in particular because of the complexity with sub-contractors. All other ones there isn't any issues because they are in-house.

You don't get to pick and choose which transactions you report to the government and which you don't based on how hard it is for you to bother with the reporting.

I'm Canadian, but not a tax lawyer. When I've done consulting work in the past for an American company, it has been done B2B; invoices were sent from my (personal) company to their company. They then paid the invoices. There wasn't anything more complicated than that; I wasn't hired as an American employee or anything like that, software development was a service that they paid my company to do and I invoiced them for it.

At the end of the year, it was simply recorded as a sale and was taxed appropriately.

Right, that's pretty much the same as my process. Did you deal with a W9? or 1099 though? Probably not because you're incorporated right.. So they listed your business. In my case a sole-proprietorship they need my personal info. Makes sense.

Sole proprietorship here too, but I've registered a company name and do all business through that. The invoices I send have the company name on them, not my personal name.