(a) An advancement is an irrevocable gift intended by the donor as an anticipatory distribution in complete or partial satisfaction of the interest of the donee in the donor's estate, either as distributee in intestacy or as beneficiary under an existing will of the donor.

(b) No advancement shall affect the distribution of the estate of the donor unless proved by a writing contemporaneous therewith signed by the donor evidencing his intention that the gift be treated as an advancement, or by the donee acknowledging that such was the intention.

(c) When so proved, the advancement is part of the estate of the donor for the purpose of distribution. If such advancement is equal to or greater than the interest of the donee, whether in intestacy or under the will, such donee or his successor in interest may not share in the distribution of the estate; but if less than such intestate share or testamentary interest, the donee or his successor in interest may take his intestate share or testamentary interest reduced by the amount of the advancement.

(d) Unless otherwise provided in a writing contemporaneous with the advancement and signed by the donor:

(1) An advancement, made as provided in this section, may be adjusted out of the property of the donor in such manner as may be equitable.

(2) The advancement shall have the value at which it is appraised for estate tax purposes, or, if not included in the gross taxable estate of the donor, the value at which it would have been appraised if included therein.

(e) Nothing in this section shall increase or decrease the elective share of a surviving spouse under either 5-1.1 or 5-1.1-A except to the extent authorized by paragraph (b) of those sections.