It appears servicing modified the billing cycle on some helocs which increased the expected payment significantly. What is the required notice that should be given to the borrower?

You mean they issued a statement with a six week cycle instead of a monthly cycle?

Yes. It is a true up situation.

What is a true up situation?

9(c)(1) Rules Affecting Home-Equity Plans
3. Change in billing cycle. Whenever the creditor changes the consumer's billing cycle, it must give a change-in-terms notice if the change either affects any of the terms required to be disclosed under §1026.6(a) or increases the minimum payment, unless an exception under §1026.9(c)(1)(ii) applies; for example, the creditor must give advance notice if the creditor initially disclosed a 25-day grace period on purchases and the consumer will have fewer days during the billing cycle change.

If a payment statement was sent at 15 days before change (say 5/15 for 6/1 payment) does that cover the required time or should a seperate notice be sent 15 days before the the 5/15 statement?

I think it is later:

2. Timing—effective date of change. The rule that the notice of the change in terms be provided at least 15 days before the change takes effect permits mid-cycle changes when there is clearly no retroactive effect, such as the imposition of a transaction fee. Any change in the balance computation method, in contrast, would need to be disclosed at least 15 days prior to the billing cycle in which the change is to be implemented.

To tag onto this thread, if we are contemplating shortening the statement mailing date from 30 days prior to due date to 20 days prior to due date, does this only require that we notify the borrowers 15 days before the billing cycle in which the change is to be implemented? I just realized the title of this thread pertains to the billing cycle, so I want to clarify that the billing cycle will remain the same and apologize for using a thread that's not exactly on my point.

I am struggling to discern if this change may be a "significant change in account terms" requiring 45 days of notice rather than 15 days. Thank you.

Any thoughts on how much notice is required to the borrowers if we change the statement mailing date from 30 days prior to the due date to 20 days prior to the due date? Thank you for your feedback.