If I pay off a guarantee for my corporation's debt, do I get to step into the lender's shoes?

Generally yes, in principle, through the legal doctrine of subrogation. A guarantor who pays the underlying debt in full is generally entitled to step into the position of the original lender and pursue the primary debtor, in this case the corporation, for reimbursement, along with the benefit of whatever security the lender previously held against the corporation for that debt, since the guarantor has effectively satisfied the lender's claim on the corporation's behalf.

In practice, this general principle is often addressed directly in the guarantee documents themselves, and lenders sometimes specifically limit or postpone a guarantor's subrogation rights until other creditors of the corporation are fully paid, particularly where multiple creditors or lenders are involved, so the guarantee's own wording, not just the general legal principle, ultimately determines exactly what a guarantor can claim against the corporation and when they can pursue it. A guarantor who has paid off a corporate debt and wants to understand their actual recovery rights should review the specific guarantee document rather than relying on the general subrogation principle alone.