1. If the firm pays advance tax on behalf of partners (if that’s what you are referring to) then it is advisable to debit the amount to respective Current account of the partners.
2. There is no distinction to advance tax and self-assessment tax as far as the firm pays the amount on behalf of partners. Once the amount is paid the amount, debit should be given to the partner's current account (preferably) and credit should have been the bank account of the firm.
3. It is advisable to maintain proper Current accounts for each partner to track the transactions between partners as individual and firm. Only items such as interest on capital, drawings, and profit/ loss will be given effect to the partner's capital account.
Please correct me if the above solution has an alternative view.