Sources with direct knowledge tell TMZ ... Britney will write her last child support check (yes, we know, it's actually going to be wired) November 15.

We're told she's been making bi-monthly payments to ex-hubby Kevin Federline on behalf of Jayden James, their youngest son who turned 18 2 months ago. She paid $10,000 at the beginning of November and will make her final $10,000 payment Friday.

Britney's lawyer, disso queen Laura Wasser, and K-Fed's attorney, Mark Vincent Kaplan, were embroiled in a legal skirmish earlier this year over how much Britney should pay and for how long. In the end, they agreed November would be the cutoff, which aligns with Jayden finishing high school.

It's interesting ... we confirmed Jayden has moved back to California from Hawaii and has seen his mom a couple times. Jayden, along with his big brother Sean Preston, have been estranged from their mom for years, but it seems the ice is thawing, at least a bit.

Britney and Kevin agreed at the time they divorced she would pay him $20,000 a month in child support, but in 2018 it went up to $40k a month ... an acknowledgment that despite their joint custody agreement, Kevin had the kids 100% of the time.

They agreed to the $20k a month after Sean Preston turned 18.