NOTE - I have corrected and clarified this post below.
CRA administers the rules for the issuance of T4 and T4A.
Both are on a CASH BASIS only.
Employers can make mistakes when issuing a T4 or a T4A.
As a sub-contractor you are well within your rights to notify your employer regarding their mistake and asking for a correction.
The administrative policy within CRA is three written notifications to your employer first. If no correction is made then you are entitled to send a letter to CRA Employer Services with proof of your three requests. A copy should be sent to T1 Matching.
In the meantime you should copy T1 matching with both your letters to your employer as well as with you CASH BASIS reconciliation.
If you have any questions or concerns about how the T4A should be prepared refer to the T4A video.
Earlier this year I shared the CRA powerpoint and transcript for the full webinar. Here is the link to my post.
It is a matter of fact and not conjecture or opinion that the T4A is prepared on a cash basis. It is my opinion that it is best to fix the original mistake rather than to compound the problem with an unrecognized and invalid work-around. In this case you will need to issue T4A’s to your sub-contractors as well. If you prepared these T4A’s on an ACCRUAL BASIS then you would only be further compounding the problem.