A retired couple came to us thrilled about their plan. For the first five years of retirement, they were going to pay zero tax. Not a little tax. None. They had run the numbers, the math checked out, and it felt like a win.

It sounds fantastic. Five years of retirement, tax-free.

But a zero-tax year is not always a victory. Sometimes it is a warning sign. And in their case, those five tax-free years were quietly setting up one of the more expensive retirements we have modeled.

The setup: how you get to zero tax

Consider Margaret and David, both 63, recently retired in Ontario. (A clearly fictional couple, but the structure is one we see constantly.) They have a Registered Retirement Savings Plan (RRSP) balance of roughly $850,000 between them, a Tax-Free Savings Account (TFSA) of about $260,000, a paid-off home, and they have not yet started Canada Pension Plan (CPP) or Old Age Security (OAS).

Their plan was simple. Live off the TFSA first. TFSA withdrawals are completely tax-free and do not count as taxable income, so for the first five years their reported income was almost nothing. The result on paper was beautiful: little to no tax owing, year after year.

"No tax, hooray." That was the headline.

The problem is what was happening in the background.

The trap: a growing RRSP you have to deal with eventually

While Margaret and David were spending down their TFSA, their RRSP sat untouched and kept growing. That feels responsible. It is exactly what most of us are trained to do: protect the registered money, defer the tax, let it compound.

But an RRSP is not yours alone. It is tax-deferred, not tax-free. Every dollar that comes out is fully taxable income. And you do not get to defer it forever.

By the end of the year you turn 71, your RRSP must convert to a Registered Retirement Income Fund (RRIF). Starting the following year, the RRIF carries a mandatory minimum withdrawal that you have to take whether you need the money or not. That minimum is a percentage of the balance, and the percentage rises every single year as you age. There is a floor, and no ceiling.

So picture where Margaret and David land at 72. Their TFSA, their most flexible tax-free buffer, is mostly gone. Their RRSP grew for years untouched, then converted into a large RRIF. Now they are forced to pull a rising minimum out of that large balance, and it stacks directly on top of CPP and OAS, which by then have also started.

Three taxable income sources, layered on top of each other, in the same years. Their income did not smooth out. It spiked.

Why the spike is so expensive

A lumpy, back-loaded income does two costly things at once.

First, it wastes their early low-income years. In their early 60s, Margaret and David had room in the lowest tax brackets and barely used it. Income that could have come out at a low rate never did. That bracket space is gone now; you cannot bank it.

Second, the later spike pushes them into OAS clawback territory. OAS gets reduced once net income passes the recovery threshold (in the mid-$90,000s for 2026, indexed each year). A large forced RRIF withdrawal stacked on CPP and OAS can punch straight through that line. Notably, TFSA withdrawals never count toward this threshold, which is exactly why burning the TFSA early was such a waste. They spent down the one account that could have kept their reported income low, and kept the one account that drives it up.

The headline was "five years of zero tax." The reality was a deferred, concentrated, higher tax bill, plus clawed-back benefits, arriving all at once later in life.

What the math actually said: smooth, do not defer

When we ran both versions through Optiml, the contrast was clear.

The fix is not exotic. It is balancing the tax across the whole retirement horizon instead of crushing it all into the back end. In practice, that meant drawing some of the RRSP earlier, in their 60s, deliberately filling those low brackets while they were open. Yes, that creates some tax in years that could have been zero. But it shrinks the RRIF before the mandatory minimums and OAS arrive, so the later spike never forms. And it preserves the TFSA as a flexible buffer they can tap in high-income years to stay under the OAS threshold.

This is the core idea behind the Minimize Lifetime Taxes strategy: the goal is the smallest total inflation-adjusted tax bill across your entire retirement, not the smallest bill this year. A close cousin, the Maximize After-Tax Estate strategy, optimizes for the largest after-tax amount you leave behind. They are distinct goals, and Optiml models each one directly so you can see which fits your priorities.

Optiml determines the optimal withdrawal sequence across every account, every year, based on your full tax situation. Using Compare Plans, Margaret and David could put the two versions side by side and see the lifetime numbers, not just the first-year headline.

Here is the shape of what that comparison surfaced. The figures are illustrative and modeled, not a guarantee.

Same couple, same savings, same retirement date. The smoothed plan left them with a lower lifetime tax bill and a larger after-tax estate. The five years of zero tax turned out to be the more expensive option.

The part most people miss: resilience

There is one more dimension that does not show up in a simple tax comparison, and it might matter most.

We stress-tested both plans with the Success Score, which runs each plan against 50 market scenarios drawn from over 50,000 generated return paths. The question it answers is simple: in how many possible futures does this plan still fully fund the life you want?

The no-tax-first plan was far more fragile. Here is why. When you concentrate large, forced RRIF withdrawals into your later years, you are depending on that big registered balance holding up right when you are required to draw heavily from it. If markets are weak in those specific years, you are selling more to meet a rising mandatory minimum, and the account drains faster. Far more of the stress-test scenarios failed for the no-tax-first plan.

The smoothed plan passed many more scenarios. By drawing the RRSP down earlier and keeping the TFSA as a buffer, Margaret and David were not betting their retirement on the markets cooperating in one narrow, high-pressure window. They spread the risk the same way they spread the tax.

Smooth income is not just cheaper. It is sturdier.

The Bottom Line

"No tax now" is not the same as "less tax over your life." A zero-tax year feels like a win, and sometimes it genuinely is. But when it comes from deferring a large registered balance into your 70s, it can be the setup for a bigger bill, lost OAS, and a more fragile plan later on.

The better move is usually to balance the tax across the whole horizon: use your low-income years on purpose, draw the RRSP before the RRIF minimums force your hand, and protect the TFSA as the flexible buffer it was built to be.

This is exactly what Optiml is built to surface. It sequences your withdrawals across every account, models your CPP and OAS start ages with the CPP & OAS Optimizer, stress-tests the result with the Success Score, and lets you put two versions of your retirement side by side with Compare Plans.

The goal was never to pay zero tax this year. It is to keep the most of your money working for you, across every year you have.

Smoothing beats deferring.