How long do requests to reduce payments on account take?

I requested to reduce payments on account on 17th January as my income this coming year is half what it what. It says "in progress". I have used the online system to check how long the requests take but it does not work for payments on account. Does anyone know how long they take? Also will I be fined for not paying the full payment on account by tomorrow? I have paid all by other tax owed. Thanks

Hi Lyn Pi,
If you done this when the return was submitted, it will be done automatically.
You can check your statement to ensure it has gone through.
Thank you.