Unused funds in an adjustable HECM line of credit grow at the current note rate plus the 0.50% annual mortgage insurance premium. That growth enlarges remaining credit. It does not pay you a coupon on money already in your checking account. Jay Zayer, a Certified Reverse Mortgage Professional (CRMP) licensed in California and Arizona, treats growth as spare capacity, not a second savings account.
The first-year disbursement cap in 24 CFR 206.25 still limits how much of a new line you can take immediately. Growth after year one can raise later availability if you left room.
What actually compounds on an unused HECM line
The note rate on a HECM ARM moves with the index and margin in the loan documents. Annual MIP of 0.50% of the outstanding balance is in Mortgagee Letter 2017-12. For unused credit, HUD’s line-of-credit formula adds a growth factor tied to that same rate-plus-MIP idea so remaining credit keeps pace with what the loan would have accrued.
Cash you withdrew stops being “unused.” Only the leftover line keeps that treatment. Principal-limit growth and line growth are related HUD mechanics. They are not a stock-market return.
Expected rate, which sets the original principal limit, is a different number from the note rate that drives day-to-day accrual. Expected rate today sits in the mid-to-upper 6% range. Do not mix it with the monthly ARM coupon.
Why first-year caps still matter if you want growth
If you drain the line at closing up to the 24 CFR 206.25 cap, you have chosen cash now over later capacity. Mortgagee Letter 2014-21 is the policy letter behind that cap. Keeping a large unused line is a deliberate choice. It is not the default on every adjustable HECM.
A LESA that earmarks funds for taxes also reduces what can sit as a growing, borrower-controlled line.
Model unused versus drawn before you pick a lump sum because a neighbor liked growth charts.
When growth is the wrong reason to wait
If a first mortgage is expensive, paying it at closing may beat protecting a growth chart. If you need cash for a roof this quarter, unused capacity will not buy shingles. Growth is a feature for households who can leave money undrawn.
Suppose the balance on a cheap existing loan is small, and a 66-year-old in Chandler wants a reserve for future care. An adjustable line with most funds unused is the structure that matches that reserve. A tenure plan is not.
Read principal limit for how the original capacity is set, and how interest is calculated for the accrual side of the same loan.
Can unused HECM credit grow if the house later sells for less than the line?
Yes, unused adjustable-HECM credit can grow while you occupy, even if a later sale would not support that paper capacity as cash. Growth is a HUD servicing formula on remaining credit. It is not an appraisal of the house. At a due-and-payable sale, heirs and the estate deal with the outstanding balance and leftover equity, not with a promise that every unused credit dollar will be delivered as a check. 24 CFR 206.27(b)(8) limits HECM recovery to the property and FHA insurance. A line that “grew” above value does not create a personal bill for heirs. It also does not create a right to draw that excess after the loan is due.
Fixed-rate HECMs usually do not keep an unused compounding line. If growth is the reason you called, you need an adjustable HECM and a payment plan that leaves capacity undrawn. 24 CFR 206.19 is the payment-plan rule. 24 CFR 206.25 is the first-year disbursement cap that can force you to leave capacity undrawn whether you wanted growth or not.
This feature does not help a household that will empty the line at closing. Nothing unused remains, so nothing compounds as credit. Accrual still increases the balance on what you took. It does not help someone who treats growth charts as an investment return they can spend twice. Growth is capacity. A draw is debt.
Here is a situation that comes up often: a 66-year-old in Chandler wants a reserve for future in-home care and can leave most of the line untouched. That is the household growth is built for. A 66-year-old who needs the first mortgage paid off and a contractor paid this quarter has chosen cash now. Keep the chart off the table.
What can go wrong: an adult child watches unused credit rise and concludes the loan is “paying them.” The funded balance is still accruing interest and 0.50% annual MIP (Mortgagee Letter 2017-12). Those are opposite ledgers. Request a statement that shows both remaining credit and outstanding balance. For the payment-plan fork rather than the growth formula, see tenure versus a line.
A follow-up: does growth continue after a due-and-payable event? Unused credit is a living-loan feature. After the loan is due, heirs deal with the outstanding balance and leftover equity, not with a compounding unused line they can keep drawing as if nothing happened. Draw before that event only if the documents still allow it. Do not plan an estate around post-death growth.