Jennifer Lopez helped Britney Spears secure a $15 million paycheck for "X Factor" -- because Britney had one intractable demand ... she had to make more than J Lo did for her first season on "American Idol."

JLo raked in $12 mil for her first season on "American Idol." There are reports she made $20 mil for the season that just ended, but we hear it's less than that.

Sources very familiar with the situation tell TMZ ... Britney's bottom line was no less than $13 mil. But sources connected with "X Factor" tell us Britney initially asked for a lot more -- $20 mil. 

As we first reported, Britney and "X Factor" eventually settled on $15 mil for the season.

The wild card now is JLo. It's unclear if "American Idol" will pay her what she's been making because ratings are down and if she can't pull in at least what Britney is getting, ego could make it a no go.

Stay tuned.

Simon Cowell and Britney Spears want TMZ to know ... despite our stories about Britney having a tough time judging "X Factor"  ... they couldn't be happier. Let's be real -- Britney says she's talking to Harvey in the video, but she's really talkin' to you.

As TMZ first reported, Britney walked off during shooting on Thursday ... leaving four contestants to sing to an empty chair. Yesterday Britney took one short break during taping, but was otherwise much more outgoing than on Day 1.

We starting poking around late yesterday because we heard rumblings that Britney might be having second thoughts, but she and Simon want to make it clear -- Britney is going nowhere.

We gotta ask ...

She's baaaaaaaaaaaaack ... Britney Spears just showed up for the second day of filming "X Factor" in Austin, Texas today --  wearing the same dress as yesterday ... for continuity.

It should be exciting ... at least if it's anything like Britney's first day -- when the singer walked off the set in the middle of auditions, disappearing for four full performances.

Some sources say Britney was upset over a contestant's rendition of her song "Hold It Against Me." Others say Britney just needed a break.

But it doesn't matter -- as we first reported, Britney's got "X Factor" over a barrel ... locking down a contract that pretty much allows her to do whatever the hell she wants.


3:37 PM PT -- That's a wrap for now. The judges just finished one of today's tapings and waved goodbye to the audience ... check out all those Apple products.

3:32 PM PT -- Britney just said yes to a contestant the other three judges rejected -- saying, "I'll sign you personally, sweetie." One problem ... Britney doesn't have a label.

2:25 PM PT -- We're told Britney has had a great start to the day and seems much more confident -- even getting so bold as to disagree with Simon. She did take one short break, about five minutes, and she missed one audition ... which everyone on set was totally ok with.

1:50 PM PT -- ALL the judges are wearing the same outfits as yesterday -- and sources tell us, the reason is producers didn't get all the shots they needed on the first day of filming ... and need to fill in some gaps.

Britney already seems to be in better spirits today than yesterday ... spotted dancing behind the judges' table with Demi Lovato with Simon Cowell sitting beside them.

The honchos at "X Factor" wanted Britney Spears so badly, they literally gave away the candy store by giving her the right to do things during production that are not "normal" ... and that includes taking breaks whenever her little heart desires.

As TMZ reported, Britney walked off the set yesterday during the first taping, leaving behind an empty judge's chair while 4 contestants did their thing.

Sources connected with the production tell us Britney was "overwhelmed" and needed to leave. People who were at the taping tell us she was upset by the audience reacting negatively to some of her comments.

Fact is ... "X Factor" wanted Britney so desperately, she was able to negotiate terms that are "unheard of" -- so say people with direct knowledge of her deal. As one source put it, "Simon is a smart and shrewd businessman who knew Britney could make his show and he was willing to give her just about anything to come on board -- and he did."

So Britney is allowed to walk off any time she wants. And that's just the beginning. Britney can do just about anything she wants ... and get $15 million in the process.

Nice work if you can get it.

Britney Spears walked off the set of "X Factor" moments ago ... and according to several people in the audience, she was upset after a contestant butchered her song, "Hold It Against Me."

Britney did not come back immediately ... and four contestants auditioned in front of the remaining judges ... and an empty seat.

Someone connected with the show tells us Britney was not upset over the song -- and that she "Just took a short break."

The show is currently on a break -- so we don't know if or when she will return to her seat.

Britney Spears' first day as an 'X Factor' judge is NOT a total disaster ... in fact, the pop star has been articulate, encouraging and even funny at times.

Audio has emerged from the first round of auditions in Austin, TX ... where Britney has been dishing out criticism from the judge's table with Simon Cowell, L.A. Reid and Demi Lovato.

It didn't take long for Britney to clash with Demi ... they disagreed with each other on the very first contestant -- one person LOVED it ... the other, not so much.


The crowd is super-pumped -- are you?

So it begins ... Britney Spears just showed up for the first day of filming for Season 2 of "The X Factor" in Texas -- wearing a slim-fitting breast-accentuating pink dress, black heels, and a big smile.

Auditions are set to kick off any minute at the Erwin Center in Austin -- and we're told Britney's fellow "X Factor" judges Simon Cowell and L.A. Reid are there too.


Demi Lovato also showed up ... and got dissed by a fan holding a sign that says, "Go Britney." 

Always tough to be last.

Britney Spears spoke to FOX cameras before she took the stage at yesterday's Upfronts ... and she did so while chewing a piece of gum. Ding dang, y'all!!!

Britney ditched the gum by the time she went in front of the advertisers ... so clearly someone caught a glimpse of Brit's red carpet faux pas and corrected it. 

For what it's worth ... Simon Cowell was chewing away too!

The gum wasn't the only thing Britney was chompin' on during yesterday's festivities -- Brit took a few bites out of her fingernails, too.

Britney Spears was off to a shaky start on "The X Factor" thanks to her nervous introduction speech -- which is either a bad thing (for her) ... or a good thing (for viewers). Or both.

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No one was more nervous to see and hear reassembled pop princess Britney Spears at her big $15 million "X Factor" announcement  yesterday than Britney herself ... at least judging from her chewed up and bloody fingernails.

Despite the unwavering support from her new boss Simon Cowell, Britney seems to be taking out her pre-show anxiety on her cuticles ... a problem she's been dealing with for years.  

In fact, Britney made a New Year's resolution to drop the habit in 2008, saying ... "Next year, I have to learn to stop biting my nails! I would like to stop worrying so much, because I worry all the time."

Simon Cowell isn't bothered one bit at the prospect of Britney Spears falling apart during a live episode of "X Factor" ... insisting whatever happens will be ratings GOLD!!

Simon was leaving ABC Kitchen in NYC last night after a dinner date with the other new "X Factor" judge Demi Lovato  ... when we asked the $15 million question -- "Are you nervous with Britney being on live TV?"

Some people are concerned about Brit because of her ongoing mental health issues ... highlighted by the fact she's still under a conservatorship. Simon is NOT one of those people.

As for dinner with Demi -- we're guessing Simon paid ... since she's only scoring a mere $1 million for the gig ... table scraps compared to Britney.