a) to get a direct debit from your own bank account like any normal person
b) to bill the taxpayer
Alan Keen and his wife Ann took option B. The real scandal is that the House of Commons Fees Office approved this transaction. Mr & Mrs Keen will no doubt defend themselves robustly, but whatever their defence is, I suspect it won't wash with their respective electorates.
The full story is in the Sunday Times. I'm not actually seeking to make a party political point out of this as I am sure there are some odd expenses which have come to light for Conservative MPs too. What this episode means is that the whole system needs a complete overhaul and it should be conducted by professional auditors from outside the Parliamentary Estate. The Fees Office has proved itself incapable of running its own affairs.