There's going to be a wedding in our family. That's right, my sister will be tying the knot in August. When Laurie first announced her engagement, everyone in the family was excited – my mother especially. "I think you should have the rehearsal dinner someplace really palatial, with five courses and dancing afterwards; then breakfast the next morning for people from out of town – and I think you should hire that amazing band that your cousin had at her wedding a couple of years ago," my mother said.

My father saw where this was going and said, "I'll give you five thousand bucks to elope."

Turns out my sister can't be bribed. A wedding it will be. I told Jim, my sister's fiancé, that life will change big-time when he's married. "Jim, I know you don't realize it, but you and Laurie are using different names for her cat; you'll need to start paying more attention to stuff once you're married," I said. "And one more thing: You'll want to learn about the tax implications of getting married." I then shared with him a few tips. Here's a primer on the pros and cons of having a spouse under our tax law.

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The definition

First, you should know that you don't have to be legally married to have a "spouse" under our tax law – although marriage will do the trick. In fact, if you've been living with someone in a conjugal relationship for 12 months or more – same sex or not – then you'll be considered spouses for tax purposes. You can ignore the 12-month requirement if you're living together and you're both parents of the same child. If you meet these tests, you have no choice but to be considered spouses by the taxman.

The pros

Having a spouse does comes with benefits – such as the ability to receive breakfast in bed (although in my case this requires sleeping in the kitchen). But there are tax benefits as well, including:

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The cons

Having a spouse can also come with tax drawbacks. Consider these:

Tim Cestnick, FCPA, FCA, CPA(IL), CFP, TEP, is an author and founder of WaterStreet Family Offices.