Usually shared
Housing, utilities, groceries, household supplies, internet, shared insurance, furniture, pets, children, travel together, and subscriptions both people use are usually shared. The exact split can still be 50/50 or proportional.
Usually personal
Individual hobbies, personal clothing, solo meals, gifts to friends, one person’s debt, personal upgrades, and subscriptions only one person uses are usually personal. Keeping them separate protects autonomy.
The edge cases
Restaurants, family events, car costs, furniture, health expenses, and “I bought this for us” purchases often need an explicit rule. If the same type of expense repeats, create a category rule instead of deciding every time.
Use consent, not surprise
A purchase should not become shared just because one person entered it into an app. If the cost is new, large, recurring, or optional, agree before treating it as a household expense.
Review the list when life changes
Moving in together, earning different incomes, having a child, changing jobs, buying a car, or caring for a pet can all change what belongs to the household.