Offer your thoughts or opinion on the input financial query or topic using your financial background.

Do I need to file taxes jointly with my girlfriend if we live together?
If you pay her rent, how do you differ from a tenant in the eyes of the law? I ask this to show that you are in a business relationship first and foremost. If you don't want to file jointly, there is nothing compelling about your situation to force it. (Grant you, in most countries, there is a benefit to filing jointly) but here, I would argue it would be difficult to make the case. There are, to the best of my knowledge, no laws barring opposite sex landlord-tenant rental situations.  Furthermore, there are no laws barring romantic relationships amongst landlords and tenants.  Indeed, you would need to prove your relationship in some fashion for it to even be considered. In establishing a date of separation from my soon-to-be-ex-wife, for example, I merely needed to prove that we were not "presenting ourselves as husband and wife."  Once I showed that we didn't sit together at church and that she was attending parties I wasn't, that was sufficient. Proving you are in a relationship is actually a lot harder than proving you're not.