Available to promise takes the simple availability calculation, adds time phasing and takes into account future scheduled receipts. Available to promise may be calculated for each day or broken down into larger time buckets. The first time period will take on-hand inventory and add any scheduled receipts for that period. It will then deduct any allocations scheduled prior to the next scheduled receipt (which may be several periods in the future). Subsequent periods without any scheduled receipts will have the same available to promise as the previous period. Subsequent periods with scheduled receipts will generally start with a fresh calculation, ignoring any remaining available to promise from previous periods. There are many variations on exactly how available to promise is calculated and it is also important to note that available to promise often works independently of allocation systems. This can sometimes create conflicts. See also Available, Allocations.