Accounting related question about bonus payment

[luxe <..hidden..>]

Hello friends,

I am a software developer working on contract.  For some time now I am
trying to grasp some basic accounting ideas and implement them with
LSMB in order to keep track of my books.  You could congratulate me
with quite of success. ;)

So far, I manage my normal process: time cards -> sales order -> sales
invoice -> payment.  But I have a special case that I am not sure how
to handle.  My client pays me a bonus one payment a year.  In effect
that is an extra payment that is not directly related to particular
work done (hours) and I do not submit an invoice for that reason.
Could somebody advise me how to enter such transaction in LSMB and how
should look like from the accounting standards point of view.  Should
it be entered as a General Ledger transaction?  If so, which account
would be debit and which credit?

Any help is greatly appreciated.

Thanks,
luxe