The phrase "a little sum" is correct and usable in written English.
It can be used when referring to a small amount of money or a minor calculation.
Example: "After reviewing the expenses, I realized that a little sum was missing from the total."
Alternatives: "a small amount" or "a minor total".
I had a little sum from my divorced husband's father, who was struggling too, so I could feed her.
"Ten yuan is just a little sum, but what really matters is an official explanation," a Mr. Zhang said.
Fifteen years ago she decided to use that space to start a business with her husband and she made a very difficult decision to borrow a little sum of money from a couple of moneylenders.
In the end, in spite of our best intentions, we couldn't resist a little summing up of the closing century: We picked the century's 10 most notable human-machine interfaces.
I was making $100 a day, which is a nice little sum of money to keep gas in your car.
Indeed, Icahn's group holds more than $2 billion worth of stock in Time Warner, which would have netted them at least $244 million–a tidy little sum in itself for a couple of weeks worth of buying and spinning.
With Dirt Music, Winton has successfully reworked that skill to write a novel so cinematic you suspect he wouldn't mind if it fetched a pretty little sum for the film rights.
Helpling, the Rocket Internet-backed cleaners-on-demand service, has tidied in a nice little sum of its own after announcing $17 million in fresh funding.
This could be something like publicbackgroundchecks, where you pay a small sum for a little bit of information.
Or, use something more comprehensive, such as Government-records.com, where you pay a small sum for a little bit of information.
Before my affairs are definitely settled in Belgium, I would not dare to use the little sum given me for specific purposes, except in a grave necessity.
