There are very few reasons for it to be acceptable to not honour a deal on The Collector Alliance. It is bad behaviour, does not honour your fellow collector, and erodes the integrity of the market. So the headline point is - you are expected to commit to your actions as detailed in our collector accords.
If there is a genuine good reason to not follow through on your commitment (and there will be very few), then the first action must be to talk to the seller you have bought the item from and request them to cancel the arrangement. If they agree, then the matter need go no further.
However, the seller is within their rights to insist you make payment and honour the deal. If you do not comply then the seller has the option to raise the matter to TCA support. The likely outcome of such an investigation is termination of your membership for life. Furthermore, we will not issue you a subscription refund for any paid time remaining. We have zero tolerance for behaviour that violates our core values.
So please consider carefully your intent to buy on The Collector Alliance. We hold all our members accountable to our core values and will not hesitate to remove people who do not share them.