The investor Kevin O'Leary says keeping a journal of your achievements at work will help you negotiate a promotion or pay rise - here's how

• Keep a journal of your work achievements if you want to get promoted, Kevin O'Leary said.
• Note down the task, the deadline, and when you achieved, he said. A pen or pencil journal will do.

If you want to get a promotion or pay rise, "start journaling now," Kevin O'Leary says.

The Shark Tank star and investor told CNBC Make It that keeping a journal of your achievements will give you more sway when you're negotiating with your boss.

"The employees in my companies that get raises, remind their bosses of all the achievements they've done over the last 12 months," O'Leary said.

Even though your boss may not remember those achievements, "you do because you're keeping every single journal entry about the tasks you were given, when they were given to you and when you achieve them - sometimes ahead of schedule," O'Leary said.

Many people are working away from head office at the moment, which gives them fewer chances to schmooze their boss, O'Leary said.

In order to get noticed, first ensure that tasks you're given are "deliverable and measurable," O'Leary said. For example, a 30-day deadline for a task, or a specific sales goal.

Then, when you've completed the task, make a record of your "executional excellence," O'Leary told CNBC Make It. "You've achieved something that was sitting out there as a marker," he said.

Write it down, and bring it up when you approach your boss for a raise or promotion, he said.

It doesn't have to be a sophisticated record - a pen and pencil journal will do, O'Leary said.

The investor is a judge on CNBC's Money Court, and like many high-profile business figures he's often asked to share his advice and lessons on how to get to the top.

He previously told Insider's Dan Schawbel that his mother's early advice to save 10% of everything you own had influenced his investment decisions throughout his career.

He's also said that true "work-life balance" is a myth, and that he only invests in entrepreneurs who don't get "flighty or emotional" under fire.