What is Tacking?

Legal Definition
Tacking is a legal concept arising under the common law relating to competing priorities between two or more security interests arising over the same asset. The concept is best illustrated by way of example.

  1. Bank A lends a first advance to the borrower, which is secured by a mortgage over the borrower's property. The mortgage is expressed to secure this advance and any future advances.
  2. Bank B subsequently lends more money to the borrower and takes a second ranking mortgage over the same property.
  3. Bank A then subsequently lends a second advance to the borrower, relying on its original mortgage.

Bank A will always have a first priority claim against the property for the full amount of its first advance. But it will be able to claim against the property in priority to Bank B with respect to its second advance only if it is permitted to tack the second advance to the mortgage that was taken at the time the first advance was made. If Bank A is not permitted to tack the second advance, then Bank B's claim in respect of the sums that it lent will have priority over Bank A's claims with respect to the second advance.

In American jurisprudence, Black's Law Dictionary defines tacking in slightly narrower terms:

1. The joining of consecutive periods of possession by different persons to treat the periods as one continuous period; especially the adding of one's own period of land possession to that of a prior possessor to establish continuous Adverse possession for the statutory period.
2. The joining of a junior lien with the first lien in order to acquire priority over an intermediate lien.

Separately, in the definition of tabula in naufragio, Black's comments:

It may be fairly said that the doctrine survives only in the unjust and much criticised English rule of tacking.

-- Wikipedia
Legal Definition
Engl. law. The union of securities given at different times, so as to prevent any intermediate purchasers claiming title to redeem, or otherwise discharge one lien, which is prior, without redeeming or discharging other liens also, which are subsequent to his own title. Jer. Eq. Jur. B. 1, c. 2, §1, p. 188 to 191; 1 Story, Eq. Jur. §412.

2. It is an established doctrine in the English chancery that a bona fide purchaser and without any notice of a defect in his title at the time of the purchase, may lawfully buy any statute, mortgage, or encumbrance, and if he can defend by those at law, his adversary shall have no help in equity to set those encumbrances aside, for equity will not disarm such a purchaser. And as mortgagees are considered in equity as purchasers pro tanto, the same doctrine has extended to them, and a mortgagee who has advanced his money without notice of any prior encumbrance, may, by getting an assignment of a statute, judgment, or recognizance, protect himself from any encumbrance subsequent to such statute, judgment or recognizance, though prior to his mortgage; that is, he will be allowed to tack or unite his mortgage to such old security, and will by that means be entitled to recover all moneys for which such security was given, together with the money due on his mortgage, before the prior. mortgagees are entitled to recover anything. 2 Fonbl. Eq. 306; 2 Cruise, t. 15, c. 5, s. 27; Powell on Morg. Index, h. t.; 1 Vern. 188; 8 Com. Dig. 953; Madd. Ch. Index, h. t.

3. This doctrine is inconsistent with the laws of the several states, which require the recording of mortgages. Caines' Cas. Er. 112; 1 Hop. C. R. 231; 3 Pick. 50; 2 Pick. 517.

4. The doctrine of tacking seems to have been acknowledged in the civil law, Code, 8, 27, 1; but see Dig. 13, 7, 8; and see 7 Toull. 110. But this tacking could not take place to the injury of intermediate encumbrancers. Story on Eq. §1010, and the authorities cited in the note.
-- Bouviers Law Dictionary
Legal Definition
The uniting securities given at different times, so as to prevent any intermediate purchaser from claiming a title to redeem or otherwise diseharge one lien, which is prior, without redeeming or discharging the other liens also, which are subsequent to ais own title. 1 Story, Eq. Jur. § 412. The term is particularly applied to the action of a third mortgagee who, by buying the first lien and uniting it to his own, gets priority over the second mortgagee. The term is also applied to the process of making out title to land by adverse possession, when the present occupant and claimant has not been in possession for the full statutory period, but adds or "tacks" to his own possession that of previous occupants under whom he claims. See J. B. Streeter Co. v. Fredrickson, 11 N. D. 300, 91 N. W. 692.
-- Black's Law Dictionary
Legal Definition
Adding together the times of two or more successive adverse possessions, the holders of which were in privity, in computing the statutory period of limitation. See 11 N. D. 300, 91 N. W. 692.
-- Ballentine's Law Dictionary