How do you split costs when someone joins a trip late?

Steps

1. 01

   Add the late joiner as a member when they confirm

   Even if they're not there yet. Adding them to the group from day one means every expense after their join date can include them.

2. 02

   Pro-rata time-based costs

   Airbnb booked for 7 nights at €1,400, but D arrives for nights 4–7 only: D pays for 4/7 of the per-person share. The remaining 3/7 split between the original group. EvenRound's 'shares' mode handles this with weights.

3. 03

   Per-expense participant selection for everything else

   Day-1 dinner: D wasn't there — leave them off the participants. Day-4 lunch: D was there — include them. The participants field is per-expense; use it.

4. 04

   Don't try to 'guess' a flat discount for D

   Tempting shortcut: 'D pays 75% of everything because they were there for 75% of the trip.' Easier in conversation, unfair in practice (they weren't part of the day-1 expensive dinner at all). Use per-expense participants.

5. 05

   Run the smart settlement at the end

   EvenRound's settle-up groups all the per-expense math into one optimal payment plan. D gets one number; everyone else gets one number; done.

Worked example

Late joiners are a feature, not a problem. Pro-rata time costs + per-expense participants gets the maths right without anyone feeling fleeced.