The 40-year-old actress feels that the pair do not need any certificate to seal their union.
Watts and Schreiber have two children together two-month-old Samuel, and 18-month-old Alexander.
There were reports that the pair had decided to take their wedding vows soon when Watts was photographed wearing a diamond on her left ring finger in March last year.
"Liev gave me this beautiful ring. We're very much together. We just don't have that certificate and that's okay with both of us. Maybe one day we'll just wake up and go, 'Hey, let's do this.' And maybe not," Watts told 'OK!' magazine.
The couple began dating in 2005.
