Morgan Stanley, the world's largest brokerage firm, fired the first shot in Wall Street's pay formula wars by telling brokers more of their pay will be deferred in 2015 than in the past.

The firm's 16,000-plus brokers, who this week were mailed their 2014 bonus totals but have not yet been told of the 2015 formula, will have from 1.5 percent to 15.5 percent of their cash and stock bonuses deferred, said a source familiar with the plan.

"In most cases, it's a very modest increase in deferrals, but without it there would be a great deal of distortion at certain revenue and length-of-service levels that the bonuses are tied to," the source said.

Brokers who produce $1.1 million to $1.65 million of revenue, slightly above average, will have 10 percent of their bonus deferred, the source said. One-fourth will continue to be paid in stock collected after four years and 75 percent in cash that vests over eight years.

Figuring out the exact change may not be easy. Broker pay manuals often run more than 50 pages and change annually based on firms' goals, such as raising the number of accounts with at least $500,000 in them.

The guides are nevertheless studied carefully by brokers and headhunters to determine where the most comfortable deals reside. Since Morgan Stanley's initial change involves making brokers wait longer to collect their pay, rival firms are likely to adopt similar plans, said Ron Eddie, president of recruiting firm Millennium Career Advisors in San Diego.

The change for next year was disclosed to branch managers earlier this week and aims to give a clearer view of what brokers will give up in deferred pay if they leave for a rival firm. Brokers next year will receive a "unified grid" that combines their annual pay with the bonuses and the total deferral amount.

"The deferrals will not be a big money saver for the firm, but hopefully you tie people to the ship a little longer," the source said.

Morgan Stanley's standard grid will continue to have 10 levels of payouts tied to total production. Brokers bringing in up to $250,000 receive 28 percent of the amount. The payout tiers up to 47 percent for those booking $5 million.

The Morgan Stanley changes were reported earlier Thursday by Investment News.