Producers must include all their production costs in their prices if they want to stay in business. The wages paid to his employees — which Douglas calls "A payments" — are only part of the cost of producing the product. The producer also has other production costs that are not distributed in wages, but which he must include in his prices: payments for materials, taxes, bank charges, machine maintenance and replacement, etc. Douglas calls the payments made to others "A payments". Douglas calls the payments to other organizations "B payments".
The product's selling price must include all costs: wages (A) and other payments (B). The product's selling price will therefore be A + B. Clearly, then, wages (A) cannot buy the sum of all costs (A + B). There is therefore a chronic lack of purchasing power in the system.
When the finished product is offered to the public, it comes with a prize. But some of the money in that price was distributed perhaps six months, a year or more ago. Another part will be distributed only after the product has been sold and the dealer has used his profit. Another part, perhaps in ten years' time, when the machine, whose wear and tear is included in the price, is replaced by a new one. And so on.
Then there are people who receive money and don't use it. (They save it.) This money is in the prices; it's not in the purchasing power of those who need the products.
Repayment of fixed-term bank loans and the current tax system further accentuate the mismatch between prices and purchasing power. Hence the accumulation of products. Hence unemployment and the rest.
Some may retort that the companies paid by the "B" payments (those having supplied the raw materials, machinery, etc.) pay wages to their own employees, and that part of the "B" payments thus becomes "A" payments (wages). This does not change the truth of what has been said earlier: it is simply a wage distributed at another stage of production, and this wage (A) is not distributed without entering into a price, which cannot be less than A + B. The gap always exists.
Even if we try to raise wages to catch up with prices, the rise in wages will automatically be included in prices, and nothing will be settled. (It's like the donkey chasing the turnip in the cartoon.) To be able to buy all the production, therefore, we need additional income outside wages, at least equal to B. This is what the social credit dividend, granted every month to every citizen of the country, would do. (Mind you, this dividend would be financed by new money created by the nation and not by taxpayers' money, which would then come from wages).
Without this other source of income (the dividend), there should theoretically be a mountain of unsold products in the current system. If the products are selling just fine, we've got a mountain of debt instead! In fact, since people don't have enough money, merchants have to encourage credit sales to sell off their merchandise. (Buy now, pay later... in 36 instalments!)