Editor's note: This is the last in a three-part series about how same-day ACH is affecting credit unions.

Same-day ACH's three-phase rollout may be speeding up payments in the financial ecosystem, but the jury's still out on whether some of that progress will come at the expense of one well-known credit union product: Bill pay. Some say same-day ACH attracts mostly business users and can peacefully co-exist with bill pay; others wonder whether same-day ACH's similar end game (quick, cheap funds movement) will water down bill pay's reach with members.

The answer may not arrive until after Sept. 15. That's when Phase II of same-day ACH's three-phase implementation plan kicks off, requiring credit unions to provide same-day ACH debit capabilities. That will allow a wide variety of consumer uses cases, such as utility, mortgage, loan and credit card payments, according to NACHA — The Electronic Payments Association. Phase I, which took effect on Sept. 23, 2016, increased the movement of funds between financial institutions to three times per day and required all receiving depository financial institutions to accept same-day transactions. On March 16, 2018, Phase III will kick in, requiring financial institutions to make same-day ACH funds available to depositors by 5 p.m. local time.