Regardless whether you or your mom requested it, the contractor acted on it because your side has agreed to it. You still have to pay him for his work done. Did you tell him not to take instructions from your mom before this?

If his work is not up to your standard and you're not happy with it, tell him to do it again or find another contractor to redo at your own cost.

As for the receipt, learn from your experiences and ask contractor if they have company that can issue you receipt first before agreeing to engage them in future.

What you mean you do not have anyone else? Where did you find this contractor? Why do you say that he is illegal?

What do you mean his saving account requested receipt?
You mean you want to report him to LHDN for not declaring his income? What proof do you have?
Like others mentioned, a lot of handyman don't really provide receipts, some are illiterate and can't read/write. Hence why you should check first if they can issue you one if it's so important to you. Sometimes you can write the receipt yourself and ask them to sign that payment received.

Not sure what you can do if you're not happy with his work ethics and workmanship, other that complain to your friends for recommending not so good contractor to you and never to engage him again.