Another sign your partner may be overspending is if you find they have bank accounts or credit cards that you weren't aware of, Nick Holeman, a financial planner at Betterment, told Business Insider in an email.
"Most accounts and credit cards have a monthly statement, or you may receive a 1099-INT around tax time from any bank accounts that paid interest," he said. "Approach financial planning from a partnership perspective, and have a direct conversation on all bank accounts and credit cards under each person's name."
This way, you can have a better understanding of your larger financial picture as a team, he added.
Andrew Schrage, CEO of the personal-finance site Money Crashers, said to be aware of new credit applications or credit cards.
"If your partner is spending recklessly, it's possible they will apply for an extra credit card or a personal loan to help cover their overspending," he told Business Insider in an email. "If you notice an unusual uptick in letters from credit card companies or promotional offers for credit, then it's possible they're trying to take on more debt."