post-mortem divorce
n. A stipulation that one must be buried separately from one's deceased spouse.
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Examples
2003
The most poignant story of the week comes from Japan where women who are trapped in unhappy marriages are secretly arranging to be buried apart from their husbands, saving money from housekeeping for a separate burial plot which can cost up to £16,000.

Haruyo Inoue, a writer who coined the term "post-mortem divorce", says: "The wives feel that they have no choice but to stay with the husband while they are alive, but in the next world they would like to get their freedom back."
—Allison Pearson, “Till death us do part,” The Evening Standard (London), February 26, 2003
2003 (earliest)
A growing number of Japanese women trapped in unhappy marriages, for whom divorce and separation are unthinkable, are opting for freedom beyond the grave by secretly arranging to be buried apart from their husbands.

"In Japan, many women stay with their husbands even though their feelings towards him are cold and they sleep in separate rooms. That way they are economically supported by their husbands," said Haruyo Inoue, a writer who has coined the term "post mortem divorce".
—Colin Joyce, “Divorce beyond the grave for Japanese wives,” The Daily Telegraph, February 22, 2003
Notes
This eyebrow-raiser of a phrase is very new, as the earliest citation shows. However, it has already been picked up by four different media sources, so it meets the minimum Word Spy criteria (at least three different articles appearing in at least three different sources written by at least three different writers).