Read the dated merchandise base
At the observed selected prices, one £4.50 tee, one £16 two-pair jogger pack and one £9 hoodie give £29.50 merchandise. The local ledger converts valid GBP input strings to integer pence before multiplying whole purchase quantities, so decimal floating-point drift does not decide whether a credit exceeds the base.
Apply the credit only to merchandise
A confirmed merchandise-only credit of £29.50 leaves £0 merchandise. A £29.51 credit exceeds this base and is rejected. This is an arithmetic demonstration, not an available voucher, gift-card validation or a promise that the retailer accepts a particular promotion.
Retain the entered charges
Shipping, confirmed additional tax and other charges remain separate after a merchandise credit. In a purely entered-charge test, £4.99 plus £1.25 still gives £6.24 payable after a full merchandise credit. Those test figures are not the observed M&S standard-delivery charge. Blank charges stay unknown rather than being silently treated as zero.
Reject unclear money inputs
The tool rejects negative values, more than two decimal places, exponent notation, fractional quantities and values above its stated input limit. Re-enter a confirmed actual quote rather than rounding an ambiguous price. It does not send an order, store payment details or collect a young person’s identity.
Apply it to the selected purchase
At a test price of £47.99 and quantity two, the merchandise line is exactly £95.98. Entering £95.99 as a merchandise credit must remain an over-credit even when the numbers look almost equal.
Sources & scope
Checked November 5, 2026. Manufacturer and retailer references support the specific statements. Dated displayed prices are not final checkout quotes, performance rankings or performance testing. This shopping reference does not replace the exact product label or retailer instructions. Current received labels and independent apparel/textile/content/commerce review remain pending.
M&S UK Powder Blue teeT874395B ↗