Short answer. The debtor, unless agreed otherwise. Article 1247 says that unless stipulated otherwise, the extrajudicial expenses required by the payment are for the debtor's account. As for judicial costs, the Rules of Court govern. So the debtor normally bears the incidental costs of making the payment.
What the law says
Unless it is otherwise stipulated, the extrajudicial expenses required by the payment shall be for the account of the debtor.
Civil Code, Article 1247 — Expenses of Payment. Read the full provision →
Payment can carry incidental costs
Paying a debt is not always free of expense. Delivering the thing owed, transporting money, or otherwise carrying out the payment can involve costs, and someone has to bear them. Article 1247 answers who does, at least where the parties have not addressed it themselves. The rule keeps the burden of getting the payment to the creditor on the side that owes the obligation, so that the creditor receives what is due without having to fund the mechanics of the debtor's own performance.
The default: the debtor bears extrajudicial expenses
The core rule is stated plainly: unless it is otherwise stipulated, the extrajudicial expenses required by the payment shall be for the account of the debtor. The extrajudicial expenses are the ordinary, out-of-court costs of making the payment. Placing them on the debtor makes sense, because it is the debtor's duty to pay, and the costs of fulfilling that duty are naturally part of the burden of the obligation. The creditor is entitled to receive the full amount owed, not a sum reduced by the debtor's cost of delivering it.
Judicial costs follow the Rules of Court
The article treats court-related costs separately. It provides that with regard to judicial costs, the Rules of Court shall govern. So when payment or its enforcement becomes the subject of litigation, the allocation of judicial costs is not decided by Article 1247 but by the procedural rules that apply to lawsuits generally. The provision thus draws a line: the everyday, extrajudicial expenses of paying fall on the debtor by default, while the costs generated within a court case are handled by the separate framework the Rules of Court supply.
Parties may shift the burden
Like many rules on obligations, this one yields to the parties' agreement. Because the default applies only unless it is otherwise stipulated, the debtor and creditor may agree to divide or reassign the expenses of payment as they see fit. Where their contract addresses the point, that agreement controls. Absent such a stipulation, the debtor should expect to shoulder the ordinary costs of making payment, and the creditor should expect to receive the amount owed without deduction for those costs.