Removing or Decreasing A/R Invoice

SUGGESTED

Hello,

I am new to Sage and have found that you can not do a JE to reduce an A/R invoice attached to a job.  My client received payment for a particular invoice long ago yet it still shows in A/R so how would I remove that invoice without voiding it?  Cash has already been posted to the checking account so ideally I would have done a JE but again Sage does not allow this.  Help appreciated!!!

Thanks!