AceShowbiz -

Beyonce Knowles and Jay-Z are finalizing a postnuptial agreement, according to Radar Online. The post-nup agreement will detail the couple's combined $1 billion fortune and how it will be divided in the case of divorce.

"They have a pre-nuptial agreement already in place, but so much has happened in terms of their empire that it's needed updating for some time," a source tells the site, "When they went through their roughest period last year, they both agreed it was time to re-clarify certain aspects of their agreement, but it's taken months to go through all their assets with a fine-tooth comb."

According to the insider, Beyonce and Jay-Z have also "negotiated 50-50 custody terms, plus trust funds for their daughter [Blue] Ivy and any future children, along with who gets what property and possessions if they separate."

The news comes after Beyonce was reportedly five-months pregnant with her second child with Jay-Z. In some pictures taken during a video shoot on January 23, the "Single Ladies" hitmaker was seen dressed in a flowing gown with a bulky hoodie atop the dress. It appeared that she tried to cover her bump with the jacket.

"It was pretty indicative she was covering up," a source told Radar at the time, "She had a dress on, but this really big black hoodie covering up. That was the outfit she used for the whole shoot. She definitely had a little belly pouch."