Third Party Rent Collector

I use a third party to collect rent online.  They hold the money for 5 days and then deposit it into my account.  If they receive payment on Dec 27th, and hold it the 5 days, then deposit it into my account in January, is this considered income for the current year (of Jan) or prior year (of Dec).  Technically it was not "available" to me until January.  I know if I receive a check in Dec and don't deposit it until January, then it's income in the prior year (of Dec), because it was "available" to me, but the third party situation seems different.

 

Thanks in advance!