Employer Matching Contributions in a Controlled Group

[AmandaJ]

Company A sponsors a plan with several participating employers - all companies are a controlled group.  The plan allocates a basic safe harbor matching contribution that is based off of annual compensation.  There is an employee who left Company A to work for Company B.

While employed with Company A, the employee contributed and was receiving the safe harbor match.  With Company B, the employee no longer deferred and therefore was not receiving the match during this time. 

When calculating the true up, is the safe harbor match calculated using total compensation from both companies, or using only the compensation from the time at Company A when contributing?

[CuseFan]

All control group participating employers are considered a single employer, so all comp (and contrib) from all employers.