Agree with Pranav as usual
The solution you are looking for: Does it conform to the pictorial representation below? You basically want “-30” against the credit side instead of “30” against the debit side when the ‘Financial Voucher’ is posted? If yes, please understand it doesn’t work like this in Accounting. (Long story). Besides, I think the confusion is only because you see the results of the posting in AX (30 and -30) on left-hand side and right-hand side (of “Amount” column and you assume its debit and credit. Correct me if I am wrong, AX doesn’t ACTUALLY say “debit” and “credit”. You just assume it is and want both entries on the right hand side of the Amount column? No use, is there?
And the second point is, if the client says main accounts should only have debits OR credits, he/she may well be right. For example, Stock Account, predominantly, should have debits on purchases (I say predominantly and NOT always because goods reversal is possible). So in such cases, if you DO NOT want to have “Plus” and “Minus” being posted all the time behind Financial and Physical Vouchers, use an ‘Inventory Control’ account of some sort to ‘temporarily’ hold stock until the full transaction is complete. In Accounting world, it is perfectly alright to have “plus” and “minus” against Control Accounts. Just not against Asset or Liability Accounts.