You have asked more questions than you may realize. For a general discussion of withholding tax accounting in Manager, see this Guide: https://www.manager.io/guides/12346. However, it applies only to withholding tax on sales and purchases. So it might cover your situation with utility bills. But the information you provided regarding these is insufficient to know with certainty.
In normal circumstances, withholding tax on your purchase of a commodity (such as electricity) from a utility provider would reduce the amount you owe to the provider. Instead of paying your full balance due, you would withhold the tax for later remittance to the tax authority. Is that what is happening? If so, follow the instructions in the second portion of the Guide above. If something else is happening, please describe such a transaction in detail. I note that having small consumers withhold tax from payments to large utility providers, making millions of consumers responsible for remittance to the authority, would be unusual. But that might be how it is done in your jurisdiction. It is also possible that you are mistaking some form of fee or tax on consumption of the commodity as a withholding tax (as the term is used by Manager) when it actually is not.
Your situation with withdrawals from a bank is entirely different. (I am assuming this withdrawal is for your own use, not a cheque written to discharge a debt of the company.) No sale or purchase has occurred. The bank has simply kept a portion of your money for remittance to the tax authority.
How you treat this depends on your income tax laws. In many countries, income of sole proprietors is taxed on the owner’s personal tax filing, not on any business filing. Payment of your personal tax due is not a transaction of the business and is not entered in Manager at all. In that situation, the payment from the business to you is a withdrawal of capital. Simply enter a payment posted to the equity account where your owner’s equity is lodged. This might be a capital account, or it could be a renamed Retained earnings account or some other form of equity account, depending on how you structured your chart of accounts. Records of withheld amounts should be kept separately, outside your business accounts, for use at personal tax filing time.
On the other hand, if local law requires the business to pay income taxes directly, the accounting differs. In that case, you are correct that such a withholding represents an asset, because it can be used to settle your income tax due just like money. So establishing an asset account (I’ll call it Tax withheld) is the right approach. When you withdraw money from the bank, enter a payment with two line items. The bank account you select on the payment form will be posted with a credit for the full amount withdrawn, making your reconciliation simple. The two line items will post the debit side of the transaction. The sum of the two line items must equal the withdrawn amount.
The first line item should be posted to the equity account holding your owner’s equity. (See above.) The amount of this line should be the amount of the withdrawal minus the amount withheld. This line item represents a withdrawal of capital, the same as in the first scenario.
The second line item should be posted to the Tax withheld account. Obviously, the amount of this line item should be the amount withheld.
Now, what happens to the Tax withheld account? When you submit your business income tax filing, you will claim the money withheld and paid on your behalf by the bank. The rest of what you owe will be paid and recorded in Manager with a payment form. Once again, break that payment into two line items.
Post the first line item to a taxes paid expense account. Make it equal to the full amount of income tax owed. Do not reduce it for the withheld amounts.
Post the second line item to Tax withheld. Make it equal to the negative of all money withheld during the tax period by the bank. This will debit the full amount of your taxes to the expense account.
The negative amount on the payment will post a credit to Tax withheld, zeroing its balance. It will also reduce the amount of the credit posted to the bank account by the amount of the previous withholdings. Make your payment to the tax authority for this reduced amount.
You will notice that no journal entries are involved in any of the processes for bank withholding or utility payment withholding, only payment forms. The only time journal entries are required in accounting for withholding tax is when your customers withhold tax on sales invoice remittances to you and instead remit tax to the authority. That is described in the initial portion of the Guide referenced above.