How can you have VAT of 15%, unless an invoice from the time when the VAT rate was 15%.
VAT is either 0%, 5% or 20%. It may say on the receipt you have that the VAT rate is 15% but wouldnt expect you would be able to reclaim it as probably VAT rate of another country.
This invoice will be outside the scope of UK VAT and so should be excluded from the VAT return (T9).
You said that it was an expense claim so I assume that it's from your colleague travelling in Europe. Subject to the input VAT rules of the country in question, it might be possible to reclaim the EU VAT - see here for more details.
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Pearce & Co - Chartered Accountant and Chartered Tax Adviser