Women in the workplace still only earn 80% of what men do, and we have a long way to go toward closing the gap, says Katie Donovan, a pay equity expert and founder of Equal Pay Negotiations, a consulting firm that works with businesses on ways to achieve equal pay for their employees.

“We have not moved the needle on the gender pay gap since the beginning of this current century and it’s estimated that we will not close it until the early part of next century,” Donovan says.

Over the course of a woman’s career, she will miss out on more than $1 million if she’s not negotiating to make equal or close to her male counterparts, Donovan says.

“It’s not just that base salary. It’s your end-of-year bonus, your Social Security, your 401(k)—there’s a lot of things that use salary in the math of what you’ll make in your career,” Donovan says.

That’s why it’s so crucial to negotiate and ask for more, Donovan says.

“Negotiation is the one thing we women can control, and it’s also expected: 84% of hiring managers expect negotiation,” she says. By accepting the first offer you get in a job negotiation, not only are you leaving money on the table, but you will be underpaid for the job you’re doing, she says.

“Think of negotiating as so elemental in hiring—it’s like going for an interview where you wouldn’t show up without your resume, so don’t accept a job without negotiating,” Donovan says.

Here are her tips for acing your negotiation and walking away with the salary you deserve.

Start before you think you need to

If you want to get ahead, you need to think ahead.

“My number one tip for negotiation is start looking for your next step in your career while you’re still happy with your current job,” Donovan says. If you’re being underpaid or want a raise, think ahead before you feel stuck.

“If you’re not being paid appropriately, it’s not your fault and it’s not your job to figure out how to make your employer pay you right—leave and find someone who will pay you right.”

Know the job’s worth

Donovan says it’s important to make a negotiation as objective as possible, so instead of asking, what is my worth, ask what is the job’s worth. This way, you’re not making the negotiating personal, and are focusing on the market of the job instead.

“The value of your job is really important and it will change as you change jobs and it changes every year,” Donovan says.

Visit websites like Payscale or Glassdoor, or talk to headhunters. Doing research will not only make you more prepared for a negotiation, but will help you approach it in a less emotional way, Donovan says.