What this choice actually costs you
What $50,000 parked against the loan actually does
Priya and Josh owe $500,000 at 6% over 30 years: repayments of about $2,998 a month, and a scary total of roughly $579,000 in interest if they just pay the minimum. They also hold $50,000 in savings.
Park that $50,000 in an offset (or as extra repayments with redraw) and interest is charged on $450,000 instead. Keeping the same monthly repayment, the loan is effectively cleared in about 23 years instead of 30, and lifetime interest drops to roughly $383,000. That is close to $195,000 saved: from money they still own and never handed over.
This saving is identical for both facilities. Banks market them as different products, but the compounding engine is the same. Every other difference on this page is about what happens when life changes, and that is where borrowers actually lose money.
Why offset beats a savings account even at a lower headline rate
Suppose that $50,000 could earn 4.75% in a high-interest savings account instead, $2,375 a year. Sounds comparable to the $3,000 of mortgage interest it cancels in the offset. It is not, because the ATO taxes savings interest as income while interest you never pay is not income at all.
On a 30% marginal rate plus 2% Medicare levy, the $2,375 shrinks to about $1,615 after tax. The offset's $3,000 stays $3,000. The offset effectively pays a guaranteed, tax-free 6%: nearly double the after-tax savings rate, with zero risk.
The one honest caveat is the fee. At $395 a year, an offset needs an average balance of about $6,600 at 6% just to break even. Below that, a fee-free redraw or plain savings account genuinely wins. Above $20,000, it is not close.
The redraw tax trap that surfaces years later
Here is the scenario that fills accountants' inboxes every July. A couple pays $100,000 extra into their home loan via redraw. Years later they upgrade homes, keep the old place as a rental, and redraw the $100,000 for the new deposit. The ATO's view: that redraw is new borrowing for a private purpose, so the interest on that $100,000 slice of the rental loan is never deductible again.
On $100,000 at 6%, that is $6,000 a year of interest that stops being deductible: costing roughly $2,280 a year at a 38% marginal rate, every year the loan runs. The identical move with an offset costs nothing: withdrawing your own account balance is not borrowing, the loan stays untouched at $500,000, and every dollar of its interest keeps its rental deduction.
The practical rules: if property investment is even a maybe, keep spare cash in offset, not redraw. Never mix personal and investment redraws on one loan. And if you are already deep in redraw and plans have changed, see an accountant before you touch the money: loan splitting can sometimes contain the damage, but only before the withdrawal.