A running tab, not a spreadsheet
Make one account for your friend group and keep adding: the concert tickets, the taxi home, the group gift. Hisaab Kitaab keeps the balance so nobody has to remember who covered what.
Nobody has to sign up first
Add friends by name and share a link to the balances. When they're ready, they sign up with the email you invited and take over their place, with everything already recorded for them.
Split it the way it happened
Equal splits for the pizza, exact amounts when someone only had a drink, and itemised bills for the big dinner, with tax and tip shared in proportion.
Reminders that aren't awkward
When someone owes you, send a reminder from the app or a pre-written WhatsApp message. Hisaab Kitaab limits reminders to one a day per person, so nobody gets nagged. When they pay, they record it and you confirm.
Pay in the app you already use
Add your PayPal, Venmo, Cash App, Revolut, Monzo, Wise or UPI details once. Friends who owe you get a button that opens the app, with the amount filled in where the app allows it.