Trying to pay taxes but balance not reflecting

Hello, this is my first year where i have to pay a bit of taxes, I don’t owe too much but I owe a little more than i’d be able to pay at once so when i filed i also applied for a pre-assessed payment plan which is still pending and my balance isn’t reflecting what I owe. Yesterday made 21 days which was the estimate, what should I do? do i just start paying before the payment plan is approved and when im done paying forget about it? or should I wait until it post to my account and my payment plan is accepted to start paying. I don’t owe too much just more than i’d pay at one time, I was looking to knock it out the way relatively quickly and not take up the entire 6 months so i’m just curious whether i start paying or wait. Is this type of delay normal?