Now that their marriage is officially official, Heidi Montag has formally taken Spencer Pratt's last name.

"When we filled out the marriage license, I checked the box to change my name to Heidi Pratt," she told Us Weekly in a Tuesday report. "It's on my new license, credit cards and everything."

The Hills couple wed late last month in Pasadena, CA after they had previously eloped in November and were "wed" during a 15-minute ceremony in Cabo San Lucas, Mexico.  However after it occurred, the couple acknowledged the Mexican ceremony -- which was allegedly a spur of the moment decision -- was not legally binding in the United States. 

While their first wedding was impromptu, Heidi said she's a stickler when it comes to "tradition" -- hence the reason for the name change.

"Now that we're legally married, I wanted to do the right thing," she told Us. "I want us to be a family in every way. When we have kids, I want us to all have the same last name."

Heidi said she plans to "wing it" when it comes to using Pratt professionally -- but she added her Montag moniker might still be around for her upcoming album.

"When I did my album, it was still pre-wedding, so I may still be Heidi Montag there," she told Us