I used to work for the Central Recovery Group, whose job was to get back any overpaid benefits (only a minority are prosecuted for Fraud), I'm not sure if CRG exists any more but they dealt with the whole country. Originally, I would input the overpayment details on to the computer systems, the target was to input 100 cases a day, and there were about 10 of us doing this every day! This generated letters to "our customers" informing them how to pay back their overpayment, these would usually come back as "not known at this address".My view remains that these people do it for the money. So hit them in the pocket. It was money that motivated them, and a financial penalty will help to deter them.
So another section of about 10 people would work full-time tracing people. I then moved to this section and people could be traced using their national insurance numbers to where they worked, in the vast majority of cases it turned out that they were still at the original address. But imagine the time and money it cost to establish this.
I then ended up on the section where we would negotiate with customers to repay their overpayments. A minority would offer a reasonable amount and, hopefully, would set up a direct debit so that the overpayment would start to be repaid. The majority would haggle for the lowest amount possible, some even at one pound a week. Even then there was no guarantee that they would actually keep to this repayment, they would pay for a couple of weeks then leave it, then make another payment here and there. Again, think of the time and money spent sending reminders to these people. Only a minority would end up with an attachment of earnings.
Whenever they stopped working and returned to benefits, their overpayment would return to the D.W.P., who would make deductions from their benefits. Bizarrely, this is a quicker way of getting the money back! If they came off benefits, the overpayment would return to CRG, who would write again (and post would be returned again, so the whole saga starts over). Nobody was ever visited in person by C.R.G but we would have a team in the evening who tried ringing customers. Bailiffs were never used, can you imagine a credit card company behaving like this?
I agree with you that someone convicted of benefit fraud should stop receiving benefits till they have repaid their ill-gotten gains, although I've seen repayment agreements which would take 50 years before being paid off. But this will never happen! So whenever, you see a case where the defendant is going to pay back the overpayment, just think on about how little they will pay and how long it will take. Essentially they have got interest free unsecured loans and they can pay back as and when they feel like it. Even with deductions from benefits they can ask (and get) reduced deductions as they usually have a load of other debts which they have no intention of paying.
Benefit thieves should have to repay twice what they've stolen, and should not be eligible for any further benefits – including tax credits - until they have. A confiscation order should be automatic and immediate.
If you don't punish people who are convicted of an easy crime, the offence will continue to look attractive.