The mature size for Koreanspice Viburnum (Viburnum carlesii) is usually 4–6 feet tall and 4–7 feet wide. Although it's not necessary, pruning helps to promote a well-branched shrub that has a denser growth habit. Light pruning can be performed any time throughout the growing season, but late winter or early spring is the best time to complete a hard pruning if needed. Suckers growing at the base of the shrub can be removed at any time.

Since it blooms on old wood, pruning it now will cut off the newly forming flower buds for next spring.  You will probably not get flowers in the spring, but otherwise it will not damage the plant.

Hope this helps.  Thanks for contacting Ask Extension.