Start with the ordinary selected basket
One of each selected bag gives£26.75 ordinary merchandise. The ledger validates the entered GBP strings and uses integer pence before multiplying whole bag counts. It does not substitute the Catsan Clubcard price unless you deliberately enter an actually applicable confirmed quote.
Allow an exact merchandise credit
A merchandise-only credit of£26.75 leaves exactly£0 merchandise. A£26.76 credit exceeds this base and is rejected. This demonstrates arithmetic,not a live coupon,gift-card check or promise that a retailer will accept an entered discount.
Retain additional charges
Delivery,actual additional tax and other charges stay separate. A test entry of£4.99 shipping plus£1.25 additional charge still leaves£6.24 payable after a full merchandise credit. These are test inputs,not Tesco’s observed fee schedule. If any charge is blank,the full total remains unresolved rather than silently adding zero.
Reject ambiguous inputs
Negative money,more than two decimal places,exponent notation,fractional bag counts and values above the stated limit are rejected. Do not add VAT twice to an already tax-inclusive quote. The tool neither sends an order nor stores addresses,payment details or animal health information.
Apply the distinction to a purchase
The boundary test 47.99 GBP times two equals 95.98 GBP exactly. A 95.99 GBP merchandise credit must still be rejected,while 0.10 GBP times three can accept exactly 0.30 GBP credit without floating-point drift.
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 veterinary/material/content/commerce review remain pending.
Tesco UK Catsan Hygiene20L product260814123 ↗