Treatment of loan/vouchers

My client is needing to invest in new machinery and to raise funds is considering inviting individuals/companies to invest over a period of 3 years. During that 3 year period any amount invested would accrue a nominal rate of interest which will be paid half yearly in vouchers that can be exchanged for goods. The vouchers would have a life of one year at what point they would expire The capital amount of the loan would be repaid in full after the 3 year term.

My client has put together an agreement which a solicitor has approved.

Has anyone come across this before? How have you treated the obligation for the vouchers?

Any comments appreciated.

Thank you