Visitor Visa for Parents rejected on economic and personal circumstances

[npannpl]

A relative of mine applied for 2 months visitor visa of his parents who have already been to the UK from June 2012 to October 2012. It was a standard visitor visa application for family visit.

The parents both are in their 60s and live a semi retired life with a airbnb style room they let out to visitors and make a small monthly earning of about £200 on average although since it's a seasonal thing, it can fluctuate between months.

The reason for rejection was in the 3 months bank statement, 3 transactions worth around £600 were made and the Entry Clearance Officer said that they were unable to form an assessment of the personal and economic circumstance in the home country due to the lack of declaration of the source of those 3 funds. Because of this, they were not satisfied that the applicant had given given a genuine circumstance and hence they thought that the application were not genuinely seeking entry or will leave at the end of the period of visit. The application was refused under V4.2(a) and (c) of the Immigration Rules.

So the relative wants to re-apply for his parents but provide a few more documentary evidence for those approx. £1800. The only difficulty is a lot of the transactions are still done in Cash in the home country and while there are receipts for some, not all the transactions have one. So I was wondering what would be a good way to explain or prove that to the home office or is there anything else that needs to be considered for the Entry Clearance Officer to feel it is genuine. They have got an accountant back in the home country to verify these financial transactions. Is that enough?