Lawyers and accountants often push their clients to plan for unpleasant events. Better to be prepared now than to pay the consequences later. But the Republican tax law that took effect in January has added a new urgency for wealthy Americans contemplating divorce.

Several key changes in the law may determine whether it is better to complete or update a divorce agreement by Dec. 31 or wait until the new year.

One of the biggest changes affects alimony, which will not be a tax break for Americans whose divorce agreements are completed or updated after this year. The new tax law is also causing parting spouses to look more closely at benefits for their children and the values of privately owned businesses and partnerships.

There is a lot of money at stake for wealthy couples. Nearly 600,000 taxpayers claimed alimony deductions totaling more than $10 billion for the 2010 tax year, according to the Internal Revenue Service.