Separate checks

When my adult daughter & I traveled last year, we used the Splitwise app. It was very easy to keep track of how much we each had paid. It’s great if they’re okay dividing the bill in 8, but it also will work on the app for individual cost in a bill for a restaurant, etc.

Asking for separate checks isn’t really a thing here in Portugal. When I go out with a large or small group of friends, we split the check evenly. We pay with cash or someone requests to use their CC, then we all pay that person. Cash is used much more extensively than in the US. It’s changing somewhat and CC’s are widely accepted. But, I use cash significantly more than when I lived in the US.

Bring a debit card with no foreign transaction fees and it’s very simple to get cash using the Multibanco machines. Make sure they say Multibanco, though, as the Euronet machines are everywhere and charge significant fees.

It's handled differently between Europeans and Americans.
With European friends, checks are split evenly, the idea being that everyone has chosen what they wanted and is satisfied with what they ate; difference in cost isn't a consideration.
With a group of Americans living in my city, each one goes up to the waiter or bar, states what they or their couple ate, and pays separately. It hasn't been a problem. I don't know if that would fly in Portugal, though.
Edit: In Europe, we often do as Sam writes below.

Bottom line is, no, we never ask for separate checks in
Europe.

This is how we handled it recently in Barcelona. 6 friends had dinner, we all ordered different items, but comparable, and 5 bottles of wine, which some drank more and some less. Bill came, we added appropriate tip and divided by 6 to a nice even figure. Gave the waiter 3 credit cards and he charged one third of the total to each credit card. That was easy. 8 adults should be able to handle that without someone saying "but my salad was only 6 EUR and your salad was 8 EUR."

Even here in the US, many of us just split the bill evenly.

With only one bill, it is something that should be discussed prior to the trip among those going so everybody is aware of how it will be handled. That could prevent some misunderstanding, especially if one couple doesn’t drink while another drinks a lot.

One a recent trip with another couple, one person paid the bill for everyone. A very loose tally was maintained to keep track of expenses. For us, an approximate figure of who paid what was all that was needed. With some couples we know, they’d want a figure that was down to the cent.