Guides

Tracking split expenses

Shared money comes in two shapes, and Duration gives each its own tool. Getting the split right starts with telling them apart:

• A joint account you both fund. Rent, utilities, the shared groceries — real money you pay in and steward together. That account isn’t off-budget: it’s yours in proportion to what you put in. Track it in its own Household Book — a second Book you own, kept apart from your personal money.
• Costs you each front from your own accounts. One of you buys the dinner, the other the kids’ shoes, and only the net between you is shared. There’s no joint account to track — just a running tab. Model it as a receivable on your personal book, and settle up now and then.

Most households run both at once — a joint account for the fixed bills, and a tab for everything ad-hoc. If that’s you, read both halves; the approach we use at the end puts them together.

The joint account: a Household Book

If you and your partner pay shared costs from a co-owned account, that account belongs on budget, not beside it. Its balance and the costs it pays are yours in proportion to your contribution — nothing has left your decision space; the decision is simply made jointly. Leaving it untracked would hide your household’s largest flow, and every shared sinking fund with it — the roof repair five years out is exactly the money the two-axis model is for.

So give it its own Book. A Book is a separate set of accounts and buckets you own and switch between; the joint account lives in one of its own, apart from your personal money.

1. Open the Book switcher at the top of the nav and choose New book…. Name it for the household (say, Household).
2. Switch into it and add the joint account as an ordinary account, homed at out-of-pocket. It’s a tracked account — it reconciles against its own bank statement at 100%, imports like any other, and its funds sweep to their horizons like any other.
3. Give the shared costs buckets — Rent, Utilities, Groceries, and a sinking fund or two (Roof, Car) homed wherever their horizon sits.
4. Record each partner’s monthly transfer into the account as income in the Household Book, when it lands — that’s what funds the buckets. Allocate it the way you would any income.

Now switch back to your personal Book and record your own monthly contribution. Here it’s an ordinary spend — money that leaves this book for the household — debited from a Household bucket you allocate to each month, not a transfer and not excluded from your spending. It’s likely your single largest legible commitment, and it belongs in your own spending signal. (It runs the opposite way from a receivable, which is money owed to you; don’t conflate the two.)

The two books never touch. Every unit of money lives in exactly one of them, each keeps its own clean picture, and the switcher is how you move between them. Your contribution leaving your personal book and arriving as income in the Household Book are two separate entries — Duration doesn’t link them, and doesn’t need to.

The running tab: a receivable

The other half is the money with no joint account behind it. One of you fronts the groceries, the other the dinner out, a settle-up app (Spliit, Splitwise — or a note on the fridge) keeps the running balance, and every so often someone pays the difference. Duration mirrors that rhythm with one receivable bucket per person — a running tab of what they owe you — and there are only three moments where you record anything:

1. You front a shared cost — split the transaction: your share to its bucket, theirs to the receivable.
2. Your partner fronts a shared cost — record nothing.
3. Someone settles the balance — split the settlement payment, and every figure closes at once.

Set up the receivable

1. Go to Buckets and add a bucket.
2. Give it the person’s name (say, Sam) and set its kind to Receivable.

Keep one receivable per counterparty, so each tab is legible on its own. A receivable lives at out-of-pocket, is excluded from your allocated figure, and is carved back into the drift signal — so what Sam owes you never reads as a hole in your own budget.

1 — You front a shared cost

Say a grocery run of 800 goes on your card, split evenly. When the line arrives in the import queue — or from Activity → ⋯ → Split — split it across two legs:

(Amounts in this guide are plain numbers — read them in whichever currency your Book keeps.)

• Groceries — 400, your share, ordinary spending from your own budget.
• Sam (the receivable) — 400, their share.

It stays a single event with one cash leg, so the one line on your statement still reconciles. Sam now shows 400 owed to you, and drift is unmoved — their share was never your money to fund. Front more shared costs the same way and the tab simply grows.

2 — Your partner fronts a shared cost

Record nothing. The money never touched your accounts, so there is no bank line and nothing to reconcile. Your half of that spending enters your budget later, when the balance is settled — the same record-it-when-it-lands rule Duration follows everywhere. The settle-up app is where the expense is logged for now; that is the system holding the running balance.

3 — Settle up

Suppose that since the grocery run, Sam has fronted 1 000 in gifts for the kids and 1 400 on dinner out. Your halves are 500 + 700 = 1 200, and Sam already owed you 400. The settle-up app nets it out: you pay 800.

When that payment appears on your statement, split it — one positive leg per category, read straight off the settle-up app’s expense list, plus one negative leg on the receivable:

• Gifts — 500, your half of what Sam fronted.
• Eating out — 700, likewise.
• Sam (the receivable) — −400, what Sam owed you, collected by netting.

You type those signs into the split editor as written — a plain amount for each category, and a literal minus in front of the receivable’s. Duration never flips a sign for you; what you enter is what posts. A leg’s sign is read relative to the payment: this payment is money leaving your account, so your consumption points the same way (the positive legs) and the collected debt points against it (the one negative leg).

The legs sum to exactly the 800 payment. The negative leg is the whole trick: because you paid the net, part of your consumption was covered by the 400 Sam already owed you, and the −400 collects that debt inside the payment instead of waiting for cash that will never arrive separately. Afterwards the receivable reads Settled, your buckets carry your halves as ordinary spending dated on the settlement day, and drift never moves.

(Hand-entering instead of importing? Record the payment as a plain Spend for the net amount, then split it from Activity.)

Why the amounts always close

The settle-up app computed your payment as (your halves of what they fronted) − (what they owed you) — exactly the two figures the split asks for. Enter your halves from its expense list, set the negative leg to the receivable’s current owed to you figure, and the remainder reaches zero by construction. Nothing is ever left over, and nothing goes to ready-to-allocate — a settlement is consumption plus a collected debt, never income waiting for a job. If the remainder does not reach zero, the split has caught a real bookkeeping gap — usually a cost you fronted but never split into the receivable.

When the payment goes the other way

Sam pays you the net. Split the incoming line the same way, mirrored: a positive leg on Sam clearing what they owed, and a negative leg per category for your halves of what they fronted. The signed legs again sum to exactly the deposit.

And yes — you really do type the category amounts with a minus in front here, even though a category is usually spending. The rule from above still holds: a leg’s sign is relative to the event, and this one is money in, so your shares point against it. The table below lays both directions side by side.

The sign rule at a glance

One rule covers both directions: the total is the cash that actually moved, and the legs are signed shares that add up to it. What you type differs only because the cash flows the opposite way — but what lands in your buckets is the same either way.

The last two rows are the whole point: the outcome is identical — your spending buckets drop by your shares, and the tab settles — no matter which way the cash moved. Only the sign you type flips. And you don’t have to hold that in your head: the split editor prints a live line under each amount — “Eating out falls by 700” — so you can read the effect straight off instead of reasoning about the sign.

When there is nothing to net

A plain repayment with no partner-fronted spending to book: categorise the incoming payment straight into the receivable. Partial is fine — whatever arrived clears that much, and the rest stays owed. And if you simply owe Sam with nothing owed back, record the payment as a spend against the receivable.

One nuance to know. Direction affects your spending figures. When you pay the net, your halves are legs of a spend, so they count in spending activity and averages. When Sam pays you, the netted halves ride on an income event — your bucket balances fall, but they are not your outflow, because the money never left your account. That is the honest trade, and it cannot be traded away: partner-funded consumption is visible in your buckets, never in your spending.

Starting from a messy history

If you adopt this flow with a tab that already has history — typically because shared costs you fronted were booked whole to your own buckets, with no receivable leg — your first netted settlement will not close: the buckets are overstated by your partner’s halves, and the receivable understates what they owe you by the same amount.

The clean fix is a one-time true-up before the first netted settlement, so the accumulated error never touches a real settlement. Check what the settle-up app says they currently owe you, then record a batch allocation that brings the receivable to that figure:

• Sam (the receivable) — −(the difference), raising what the tab shows owed to the true balance.
• The bucket that over-absorbed — +(the difference), restoring the budget that paid for their halves. If the history is untraceable, point this leg at a dedicated Shared adjustments bucket instead — not a real category, so six months from now the write-off still reads as what it was. (Or leave the counter-leg out entirely and the difference lands back in ready-to-allocate, yours to re-allocate.)

It is an envelope-only move — no cash, drift-neutral. From then on every settlement closes to the last decimal, and a nonzero remainder means a fresh mistake worth finding, not old sediment.

If you would rather not true up separately, the same correction can ride inside the settlement itself: add one signed adjustment leg to the split — pointed, again, at the over-absorbing bucket or at Shared adjustments, not at a live spending category.

The approach we use

The two tools aren’t rivals — most households, ours included, use both, and it’s worth seeing them side by side. We split shared money along one line: fixed and recurring goes through a joint account; ad-hoc we each front and settle later.

• The joint account is a Household Book. Rent, utilities, insurance, the weekly grocery shop — the predictable bills — are paid from a co-owned account we both fund. It’s a second Book: the account is tracked there, each contribution lands as income, and the shared sinking funds (a Car fund, a house-repair fund) are ordinary buckets that sweep to their horizons. Each month I record my transfer into it as a plain spend in my personal Book, out of a Household bucket. That one line is the whole household commitment as far as my own budget is concerned — legible, and never off to the side.
• Everything ad-hoc rides a receivable. The dinner one of us grabs, a birthday present, a taxi — costs that never touch the joint account. We keep the running balance in a settle-up app and hold one receivable bucket for my partner. When I front something shared I split it (my share to its bucket, their share to the receivable); when they front something I record nothing; every month or two we settle the net with one signed split.

The division is the point. The joint account handles the money that’s genuinely ours and deserves to be on budget with its own buckets and sweep; the receivable handles the money that stays mine and theirs and only nets out. Neither pretends to be the other, so each stays exact — the Household Book’s balances reconcile against a real statement, and the receivable settles exactly.

Where you draw the fixed/ad-hoc line is yours to set; some households run almost everything through the joint account and barely touch a receivable, others the reverse. The tools don’t care about the ratio.

Why this stays honest

Every move across both tools is an ordinary, drift-neutral event — a contribution recorded as a spend on one side and income on the other, a split spend, a signed settlement leg. Nothing is a special shared-money primitive. The Household Book is just a Book, scoped and swept like your personal one; the receivable is just a bucket. And there is no linked-pair object tying a cost to its repayment: a receivable rises when a partner’s share is categorised into it, and falls when a repayment is — whether that repayment arrives on its own or netted inside a settlement. That is what lets one receivable absorb any number of shared costs, and one split settle them all.

Last reviewed: July 2026.