Disclaimers are governed by G.L.c. 191A. Essentially, if a party who has inherited property or acquired title by way of gift or survivorship (joint tenancy and tenancy by the entirety) properly and timely disclaims an interest a "fiction" arises, which is applied as though the disclaiming party had predecease the party from whom the property interest was acquired. This "fiction," when applied sometimes can give results that may be unexpected. For example, if the sole devisee under a will disclaims, title to the disclaimed property may not fall into the residuary clause or pass intestate; if the disclaiming party had issue title would pass to them under the anti-lapse statute (assuming there is a blood relationship between the testator and the disclaiming party).
The conservator of a ward can disclaim property, provided that the conservator obtains court approval to do so. G.L.c. 191A, §2.
With regard to disclaimers concerning jointly-owned property, the statute permits for the disclaimer by a joint tenant "except that a surviving joint tenant . . . may not disclaim that portion of an interest in joint property . . . which is allocable to amounts contributed by him or her to the interest in such property." (Emphasis added.) Id. The wording of the statute suggests that the amount which cannot be disclaimed is not simply the dollar amount of contribution made by the surviving joint tenant, but extends to the proportional value of the interest in the property which corresponds to that contribution. The contribution could include both the original contribution as well as any contributions made thereafter. It is unclear, however, whether payments by the deceased joint tenant of such items as utilities, taxes maintenance and repair—which each co-tenant is severally bound to assume—would have any effect on the calculation of the amount which cannot be disclaimed (which is determined based upon contributions "to the interest in such property.")