Menggunakan SQL JOIN dan COUNT

Jika OP ingin memasukkan informasi tambahan (agregasi tambahan, dll...) menggunakan data dari users tabel:

SELECT `users`.`id`,
       count(`receipts`.`uId`)
FROM `users`
INNER JOIN `receipts` ON `users`.`id` = `receipts`.`uId`
GROUP BY `users`.`id`
ORDER BY count(`receipts`.`uId`) DESC

Jika tidak, hanya receipts tabel diperlukan...

SELECT `users`.`id`,
       count(`receipts`.`uId`)
FROM `receipts`
GROUP BY `receipts`.`uId`
ORDER BY count(`receipts`.`uId`) DESC