How to split a deposit that was paid unevenly

Whoever put in more gets more back, in the proportions they actually paid, and that stays true no matter how the rent has been split since. A deposit is a lump of money lent to the landlord by particular people, and it is returned to those people — the monthly arrangement is a different agreement about a different thing.

Write down who paid what, on the day

This is the whole article. A deposit paid in a rush, from one account, with a vague plan to even it up later, is the single most common shared-money dispute at the end of a tenancy — not because anybody lies, but because eighteen months is long enough for two honest people to remember different figures.

One message, on the day, naming who transferred what, settles it permanently.

Deductions come off the shared part first

When the landlord takes something out, most households split the deduction the way they split the rent, then return what is left in the proportions the deposit was paid. Damage to one specific room usually comes off that person's share before anything else is divided.

Evening it up early is worth considering

Where one person fronted a much larger share, some households have the other pay them back over the first few months, so that by month four the deposit is held evenly and there is nothing to remember at the end.

It costs nothing and it removes a conversation that otherwise happens at the worst possible moment — while everybody is moving out.