If you don’t have an overdraft, yes it will be declined if the funds are in a pot.
Safe to Spend’s functionality expanded over the years to do some really complex things in a really simple way, which is why that worked for you with Simple. That functionality isn’t currently available with Monzo.
You can segregate your money, but that’s about where the power of Monzo’s pots ends. There’s not much you can do with that segregated money, until you transfer it back into your actual account. They’re more like mini savings accounts but without interest. You’d have to withdraw the money from the pot before the payment was taken.
What safe to spend was doing was looking ahead, predicting your rent amount and due date, and subtracting the total from your balance before you’d paid it and assigning that to the relevant goal, then when it gets taken it comes directly from that goal after you categorise it. Essentially the money is still there and can be spent, it just appears like it’s segregated in the app.
With Monzo, it actually is segregated, hence the transaction would decline. I hope it’s functionality Monzo will be able to mimic someday. It’s something I’d really love to have.
No one other than Simple, as far as I know, does it like that, which is a shame, because I think it’s fantastic.
I’m not too sure about the payment services available with Monzo in the US, but here, you can pay some bills like rent directly from a pot, depends on the payment method.
ETA:
What Monzo does have though, is Summary, which can sort of do what simple does, but with quite a bit of friction. It has a * Left To Spend*, but I don’t find the dial to be an accurate indicator as it looks at your spending patterns to predict how you spend, rather than focusing solely on your fixed expenses like rent. The value of the amount though, once set up, should be identical to your safe to spend balance with Simple.
You can create a budget within this that lines up with your pay day, and earmark your bills and rent payments, and Monzo will reduce these amounts from your left to spend value. This is completely separate from your account balance and in its own corner of the app though. Again though, the functionality isn’t quite as powerful as what Simple offers, and it’s certainly not as simple to use. But it’s worth playing with and seeing if it can work for you.
You can read about it here: