新买的房子贷款额减少也不一定要交税， 只要你invest your own money toward the purchase

If the Relinquished Property has a mortgage on it, then the relief from that mortgage debt (when it's paid off in the sale) is considered mortgage boot to you UNLESS:
(a) the Replacement Property is mortgaged for an equal or greater amount of debt, OR
(b) you invest your own money towards the purchase of Replacement Property to offset the

debt relief
• on the property sold.