The interest adjustment date is one of those closing costs that catches first-time buyers by surprise. It is a charge for the “gap” days between when your mortgage funds (closing day) and when your regular payment schedule starts (the IAD). Every Canadian mortgage has an interest adjustment date, and it can cost anywhere from a few dollars to over $2,000 depending on when you close.
How the Interest Adjustment Date Works
The Timeline
| Event | Example Date | What Happens |
|---|---|---|
| Closing day | March 15 | Mortgage funds; you take possession |
| IAD (Interest Adjustment Date) | April 1 | Regular payment schedule begins |
| Gap period | March 15–March 31 | 17 days of “pre-payment” interest |
| First regular payment | May 1 | First full monthly payment |
The gap between closing day and the IAD exists because Canadian mortgage payments are structured to begin on the first of the month (or a specific day). Since closing dates rarely land on the first of a month, there is always a partial month at the beginning.
Why It Exists
Canadian mortgage payments are calculated on the assumption that the first payment covers exactly one full period (one month, two weeks, etc.) of interest. The IAD makes that math work:
- You close mid-month → the mortgage is outstanding but no regular payment is due yet
- The lender charges per-diem interest for those gap days
- The IAD marks the start of the regular payment cycle
- The first regular payment covers the period starting from the IAD
Without the IAD, your first payment would need to cover a partial month plus a full month, making the payment amount irregular.
How the Interest Adjustment Is Calculated
The Formula
Interest Adjustment = Mortgage Amount × Annual Rate ÷ 365 × Days in Gap
Examples by Closing Date
| Closing Date | IAD | Gap Days | Interest Adjustment ($500K at 5%) |
|---|---|---|---|
| March 1 | April 1 | 31 | $2,123 |
| March 5 | April 1 | 27 | $1,849 |
| March 10 | April 1 | 22 | $1,507 |
| March 15 | April 1 | 17 | $1,164 |
| March 20 | April 1 | 12 | $822 |
| March 25 | April 1 | 7 | $479 |
| March 28 | April 1 | 4 | $274 |
| March 31 | April 1 | 1 | $68 |
By Mortgage Size
| Mortgage | Rate | 15-Day Gap | 7-Day Gap | 1-Day Gap |
|---|---|---|---|---|
| $300,000 | 4.50% | $554 | $258 | $37 |
| $400,000 | 4.50% | $740 | $345 | $49 |
| $500,000 | 5.00% | $1,027 | $479 | $68 |
| $600,000 | 5.00% | $1,233 | $575 | $82 |
| $750,000 | 5.50% | $1,695 | $791 | $113 |
How It Appears on Your Statement of Adjustments
Your real estate lawyer or notary prepares a statement of adjustments on closing day. The interest adjustment appears as a line item:
| Item | Debit | Credit |
|---|---|---|
| Purchase price | $600,000 | |
| Deposit already paid | $30,000 | |
| Mortgage advance | $480,000 | |
| Land transfer tax | $8,000 | |
| Legal fees | $1,800 | |
| Title insurance | $350 | |
| Interest adjustment (17 days) | $1,117 | |
| Property tax adjustment | $1,200 | |
| Balance due on closing | $99,767 |
The interest adjustment is typically deducted from the funds your lawyer has available, meaning it effectively comes out of your down payment pool. It is a cash expense on closing day.
How to Minimize the Interest Adjustment
Strategy 1: Close Late in the Month
The simplest way to reduce the interest adjustment is to close as late in the month as possible:
| Closing Date | Gap Days | Cost ($500K at 5%) | Savings vs Mid-Month |
|---|---|---|---|
| March 15 | 17 days | $1,164 | Baseline |
| March 25 | 7 days | $479 | $685 saved |
| March 28 | 4 days | $274 | $890 saved |
| March 31 | 1 day | $68 | $1,096 saved |
Practical consideration: Closing on the last day of the month is popular because the interest adjustment is minimal. However, this makes the last 2–3 business days of each month the busiest for real estate lawyers, title companies, and lenders. Closings on these days are more prone to delays and errors. Building in at least 2 business days of buffer is prudent.
Strategy 2: Negotiate the Closing Date
When making an offer, you can propose a closing date near the end of the month. However, the seller may prefer a different date for their own financial or logistical reasons. The interest adjustment cost is usually not significant enough to push back hard on closing dates.
Strategy 3: Ask About Same-Day IAD
Some lenders may allow you to set the IAD to your closing date, eliminating the gap entirely. This is uncommon but worth asking about — especially if your closing date is early in the month and the interest adjustment would be substantial.
Interest Adjustment Date for Different Payment Frequencies
The IAD affects your first payment date differently depending on your payment frequency:
| Payment Frequency | IAD (April 1) | First Payment Date |
|---|---|---|
| Monthly | April 1 | May 1 |
| Semi-monthly | April 1 | April 15 |
| Bi-weekly | April 1 | April 15 (approx.) |
| Weekly | April 1 | April 8 |
| Accelerated bi-weekly | April 1 | April 15 (approx.) |
Regardless of payment frequency, the interest adjustment covers the same gap period (closing date to IAD). The first regular payment then covers a full payment period starting from the IAD.
Common Questions About the IAD
Is the Interest Adjustment Tax Deductible?
For your primary residence: No. Mortgage interest on your principal residence is not tax-deductible in Canada (unlike the US), so the interest adjustment is not deductible either.
For a rental property: Yes. If the property is a rental, the interest adjustment is a deductible expense in the year of purchase, just like all other mortgage interest.
Does the IAD Affect Your Mortgage Term?
Yes — in a subtle way. Your mortgage term (e.g., 5 years) is typically measured from the IAD, not from the closing date. If your IAD is April 1, 2026, your 5-year term ends on April 1, 2031 — regardless of whether you closed on March 1 or March 31. This means closing earlier in the month means you pay the interest adjustment AND your term is effectively the same length.
What If You Close on the First of the Month?
If you close on April 1 and your IAD is May 1, you have a full 30-day interest adjustment period. This maximizes the cost. Alternatively, some lenders may set the IAD to the same date as closing (April 1), which would eliminate the interest adjustment but mean your first payment is due May 1.
How Does IAD Work on a Refinance?
On a refinance:
- The old mortgage is discharged
- The new mortgage funds on the refinance closing date
- A new IAD is set (first of the following month)
- Interest adjustment applies exactly as it would on a purchase
What About Mortgage Renewals?
At renewal, there is no interest adjustment. The mortgage simply transitions from one term to the next on the maturity date with no gap period. This is one advantage of staying with the same lender at renewal.
If you switch lenders at renewal, the mechanics are similar to a refinance — and a small interest adjustment may apply depending on timing.
The IAD and Your Amortization
The interest adjustment does NOT affect your amortization calculation. Your amortization schedule is based on the regular payment amount starting from the IAD. The gap interest is a separate, one-time charge.
| Component | Part of Amortization? |
|---|---|
| Regular mortgage payments | Yes |
| Interest adjustment | No — separate one-time charge |
| Your amortization start date | The IAD |
| Mortgage maturity | Based on term starting from IAD |
What to Budget For
When planning your closing costs, include the interest adjustment in your calculations:
| Budget Item | Typical Range |
|---|---|
| Interest adjustment (mid-month close) | $500–$2,000 |
| Interest adjustment (late-month close) | $50–$500 |
| Other closing costs | $5,000–$30,000+ |
The interest adjustment is relatively small compared to other closing costs like land transfer tax, legal fees, and moving expenses — but it still needs to be accounted for in your closing funds.