Start with the dated tickets
One selected offer of each gives a merchandise base of£20.69. This is an arithmetic example,not a recommended combined routine or one accepted multi-merchant order. Each seller has its own delivery and checkout conditions.
Use integer pence
The ledger stores2069p rather than relying on floating-point subtraction. A confirmed merchandise-only credit of£20.69 leaves zero merchandise cost. A credit of£20.70 is rejected because it exceeds the base by one penny. The tool does not invent a discount or apply subscription terms automatically.
Charges survive a full credit
If hypothetical additional delivery is£4.99,tax£1.25 and other charges£0.00,a full merchandise credit still leaves£6.24. Those figures are a tool example,not quoted seller fees. Already included tax must not be added again.
Unknown is not zero
Blank or invalid charge fields withhold the final total. Amounts must be nonnegative,have at most two decimal places and remain within the stated limit;counts must be whole. Before ordering,replace the dated ticket with the actual chosen checkout and read the relevant seller conditions. The local calculator sends no basket or health information externally.
A concrete decision record
For a small decimal check,three items at10p produce30p;an exact30p merchandise credit leaves zero. For a larger check,two items at£47.99 produce£95.98. These examples test the money representation itself. They do not establish that a retailer offers either price or credit,so the ledger labels them as user-entered arithmetic.
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 clinical/chemical/content/commerce review remain pending.
Boots Simple400ml selected redirect10375990/8219443 ↗
Faith In Nature400ml one-time manufacturer record ↗
Boots Nizoral2%w/w60ml10025089/2695103 ↗