Britney Spears Raked in the Cash and Spent a Fortune on Pets

The Britney Spears money train just keeps rolling along ... TMZ has learned.

Britney's conservatorship filed legal docs breaking down what she earned and what she spent in 2015, and it's a lot on both scores.

Britney made $13,395,410.53 during the 12 month period, mostly from her Vegas show. Britney made millions more for the shows, but a big chunk went for various expenses and taxes.

At the end of 2015, the docs show Britney had cash and property worth $51,141,000 ... around 5 million more than she had at the beginning of the year.

Now, how did she spend more than $8 mil? Beyond the obvious houses, cars and kids ... according to the docs, Britney also dropped $37,360 on pet care, $67,800 on massages, grooming and nails, $62,813 on wardrobe but only $537 on dry cleaning!

BTW ... the documents only reveal a portion of Britney's wealth. There are millions more in various trusts.