When it arrives and how it's paid
By law, before December 20 — a minimum of fifteen days of salary. Most employers pay it between the 10th and the 15th. If your collective contract gives you more than the legal floor, the bonus usually arrives in two installments (November and December).
Which debt to attack first
By cost, no feelings involved: revolving credit-card balances. CAT between 50% and 70%, every month. Then any open SOFOM (non-bank lender) line. Then bank personal loans. Your Infonavit loan and your mortgage are the cheapest debts you have — leave them for last.
Avalanche or snowball
Avalanche: start with the debt that carries the highest CAT. That's the math-optimal play. Snowball: start with the smallest balance; you get the satisfaction of closing an account, and that satisfaction helps you stick to the plan. If you know yourself and know you'll quit halfway, go snowball. If you have discipline, go avalanche.
When the aguinaldo isn't enough
Consider consolidating. You move card balance + SOFOM + small personal loan into a single credit at a lower CAT with a lower monthly payment. The one condition — and it's a serious one — is that you don't run the freed-up cards back up. If you're not sure you can hold that line, freeze the cards (literally, in the freezer) for the life of the consolidation loan.
What not to do with the aguinaldo
Blow it all on gifts and parties. January is the longest month of the year for a reason. Don't make extra payments to Infonavit or your mortgage while you're still carrying card debt — the CAT spread is huge and you're losing money. Don't pay the minimum on every card instead of wiping one out — the minimum is engineered so the balance never really shrinks. Crushing one card completely and paying the minimum on the others is the better strategy.