Put the promotion on a calendar
A fictional service waives a $5 monthly charge for three months and then bills the normal price. Over the first twelve months, that produces $45 of charges, assuming the account remains open and no other conditions change. In a full later year, the same monthly price produces $60.
The first-year average of $3.75 a month is accurate for that scenario, but it is not the continuing monthly tariff. Keep introductory and ongoing costs on separate lines so the temporary saving does not become a permanent assumption.
Read the eligibility dates, funding requirements, eligible products and any minimum period the account must remain open. A benefit can be reduced or reclaimed if conditions are not met. Record the exact requirement instead of relying on a short promotional headline.
For example, a fictional $20 credit requiring $1,000 of funding is a different proposition from a $20 credit without a funding condition. Moving money solely to qualify can have other costs or consequences. The credit should be entered as a conditional item, not deducted from every comparison automatically.
Consider the decision after the offer ends
Ask whether the service would still fit the intended use at the ordinary price. Include the cost of leaving, transferring or cancelling if that is part of the plan. A promotion that looks inexpensive for three months can be less attractive when the exit process is included.
Keep a dated copy of the terms and set a review before the relevant renewal or expiry. Check whether cancellation takes effect immediately or at a later billing boundary. Do not assume an unused service stops charging on its own.
The useful comparison is a timeline of cash costs and conditions. It can show a genuine saving without turning a limited offer into a general endorsement. If the decision depends on meeting a condition that is uncertain, calculate the result both with and without the promotional benefit.
