Tension reinforcement in crack width and shrinkage checks.

That's right, the position of the vertical bars will govern for checking horizontal cracking.

The tension reinforcement is whichever bars are resisting the primary bending loads, so if it's a typical retaining wall, where the soil pressure is resisted by a footing under the wall, then the vertical bars are the tension reinforcement.

Rod Smith, P.E., The artist formerly known as HotRod10

The thread title refers to "crack width and shrinkage checks" which involves two separate checks.

For the wall in a cantilever retaining wall flexural cracks will be horizontal and the vertical rear face bars will control the cracking. Shrinkage for this case should be considered in accordance with the applicable code; different codes have widely different requirements.

For restrained differential shrinkage the horizontal bars in both faces will control the cracking.

Doug Jenkins
Interactive Design Services